diff --git a/pillar/api/encoding.py b/pillar/api/encoding.py
index e10cc40f..ae161b09 100644
--- a/pillar/api/encoding.py
+++ b/pillar/api/encoding.py
@@ -1,14 +1,15 @@
-import logging
-
 import datetime
+import logging
 import os
+
 from bson import ObjectId, tz_util
 from flask import Blueprint
 from flask import abort
 from flask import current_app
 from flask import request
+
 from pillar.api import utils
-from pillar.api.utils.gcs import GoogleCloudStorageBucket
+from pillar.api.file_storage_backends.gcs import GoogleCloudStorageBucket
 from pillar.api.utils import skip_when_testing
 
 encoding = Blueprint('encoding', __name__)
diff --git a/pillar/api/file_storage/__init__.py b/pillar/api/file_storage/__init__.py
index 637963fb..fc8ec449 100644
--- a/pillar/api/file_storage/__init__.py
+++ b/pillar/api/file_storage/__init__.py
@@ -3,7 +3,9 @@ import io
 import logging
 import mimetypes
 import os
+import pathlib
 import tempfile
+import typing
 import uuid
 from hashlib import md5
 
@@ -12,7 +14,7 @@ import eve.utils
 import pymongo
 import werkzeug.exceptions as wz_exceptions
 from bson import ObjectId
-from flask import Blueprint, current_app
+from flask import Blueprint
 from flask import current_app
 from flask import g
 from flask import jsonify
@@ -21,15 +23,15 @@ from flask import send_from_directory
 from flask import url_for, helpers
 
 from pillar.api import utils
+from pillar.api.file_storage_backends.gcs import GoogleCloudStorageBucket, \
+    GoogleCloudStorageBlob
 from pillar.api.utils import remove_private_keys, authentication
 from pillar.api.utils.authorization import require_login, user_has_role, \
     user_matches_roles
 from pillar.api.utils.cdn import hash_file_path
 from pillar.api.utils.encoding import Encoder
-from pillar.api.utils.gcs import GoogleCloudStorageBucket, \
-    GoogleCloudStorageBlob
 from pillar.api.utils.imaging import generate_local_thumbnails
-from pillar.api.utils.storage import LocalBlob, default_storage_backend
+from pillar.api.file_storage_backends import default_storage_backend, Bucket
 
 log = logging.getLogger(__name__)
 
@@ -81,7 +83,8 @@ def index(file_name=None):
     return jsonify({'url': url_for('file_storage.index', file_name=file_name)})
 
 
-def _process_image(gcs, file_id, local_file, src_file):
+def _process_image(bucket: Bucket,
+                   file_id, local_file, src_file):
     from PIL import Image
 
     im = Image.open(local_file)
@@ -102,12 +105,12 @@ def _process_image(gcs, file_id, local_file, src_file):
     for variation in src_file['variations']:
         fname = variation['file_path']
         if current_app.config['TESTING']:
-            log.warning('  - NOT sending thumbnail %s to GCS', fname)
+            log.warning('  - NOT sending thumbnail %s to %s', fname, bucket)
         else:
-            log.debug('  - Sending thumbnail %s to GCS', fname)
-            blob = gcs.bucket.blob('_/' + fname, chunk_size=256 * 1024 * 2)
-            blob.upload_from_filename(variation['local_path'],
-                                      content_type=variation['content_type'])
+            blob = bucket.blob(fname)
+            log.debug('  - Sending thumbnail %s to %s', fname, blob)
+            blob.upload_from_path(pathlib.Path(variation['local_path']),
+                                  content_type=variation['content_type'])
 
             if variation.get('size') == 't':
                 blob.make_public()
@@ -172,7 +175,7 @@ def _process_video(gcs, file_id, local_file, src_file):
         'backend': j['backend']}
 
 
-def process_file(gcs, file_id, local_file):
+def process_file(bucket: Bucket, file_id, local_file):
     """Process the file by creating thumbnails, sending to Zencoder, etc.
 
     :param file_id: '_id' key of the file
@@ -227,7 +230,7 @@ def process_file(gcs, file_id, local_file):
         update_file_doc(file_id, status='processing')
 
         try:
-            processor(gcs, file_id, local_file, src_file)
+            processor(bucket, file_id, local_file, src_file)
         except Exception:
             log.warning('process_file(%s): error when processing file, '
                         'resetting status to '
@@ -243,60 +246,31 @@ def process_file(gcs, file_id, local_file):
                     file_id, status, r)
 
 
-def delete_file(file_item):
-    def process_file_delete(file_item):
-        """Given a file item, delete the actual file from the storage backend.
-        This function can be probably made self-calling."""
-        if file_item['backend'] == 'gcs':
-            storage = GoogleCloudStorageBucket(str(file_item['project']))
-            storage.Delete(file_item['file_path'])
-            # Delete any file variation found in the file_item document
-            if 'variations' in file_item:
-                for v in file_item['variations']:
-                    storage.Delete(v['file_path'])
-            return True
-        elif file_item['backend'] == 'pillar':
-            pass
-        elif file_item['backend'] == 'cdnsun':
-            pass
-        else:
-            pass
-
-    files_collection = current_app.data.driver.db['files']
-    # Collect children (variations) of the original file
-    children = files_collection.find({'parent': file_item['_id']})
-    for child in children:
-        process_file_delete(child)
-    # Finally remove the original file
-    process_file_delete(file_item)
-
-
-def generate_link(backend, file_path: str, project_id=None, is_public=False):
+def generate_link(backend, file_path: str, project_id=None, is_public=False) -> str:
     """Hook to check the backend of a file resource, to build an appropriate link
     that can be used by the client to retrieve the actual file.
     """
 
-    if backend == 'gcs':
-        if current_app.config['TESTING']:
-            log.info('Skipping GCS link generation, and returning a fake link '
-                     'instead.')
-            return '/path/to/testing/gcs/%s' % file_path
+    # TODO: replace config['TESTING'] with mocking GCS.
+    if backend == 'gcs' and current_app.config['TESTING']:
+        log.info('Skipping GCS link generation, and returning a fake link '
+                 'instead.')
+        return '/path/to/testing/gcs/%s' % file_path
+
+    if backend in {'gcs', 'local'}:
+        from ..file_storage_backends import Bucket
+
+        bucket_cls = Bucket.for_backend(backend)
+        storage = bucket_cls(project_id)
+        blob = storage.get_blob(file_path)
 
-        storage = GoogleCloudStorageBucket(project_id)
-        blob = storage.Get(file_path)
         if blob is None:
             log.warning('generate_link(%r, %r): unable to find blob for file'
                         ' path, returning empty link.', backend, file_path)
             return ''
 
-        if is_public:
-            return blob['public_url']
-        return blob['signed_url']
-    if backend == 'local':
-        bucket = default_storage_backend(project_id)
-        blob = bucket.get_blob(file_path)
-        return url_for('file_storage.index', file_name=blob.partial_path,
-                       _external=True, _scheme=current_app.config['SCHEME'])
+        return blob.get_url(is_public=is_public)
+
     if backend == 'pillar':
         return url_for('file_storage.index', file_name=file_path,
                        _external=True, _scheme=current_app.config['SCHEME'])
@@ -410,10 +384,6 @@ def generate_all_links(response, now):
     response['_etag'] = etag_doc['_etag']
 
 
-def before_deleting_file(item):
-    delete_file(item)
-
-
 def on_pre_get_files(_, lookup):
     # Override the HTTP header, we always want to fetch the document from
     # MongoDB.
@@ -587,10 +557,10 @@ def override_content_type(uploaded_file):
         del uploaded_file._parsed_content_type
 
 
-def assert_file_size_allowed(file_size):
+def assert_file_size_allowed(file_size: int):
     """Asserts that the current user is allowed to upload a file of the given size.
 
-    :raises
+    :raises wz_exceptions.RequestEntityTooLarge:
     """
 
     roles = current_app.config['ROLES_FOR_UNLIMITED_UPLOADS']
@@ -674,28 +644,14 @@ def stream_to_storage(project_id):
     assert_file_size_allowed(file_size)
 
     # Create file document in MongoDB.
-    file_id, internal_fname, status = create_file_doc_for_upload(project_oid,
-                                                                 uploaded_file)
-    storage_backend = None
-    blob = None
+    file_id, internal_fname, status = create_file_doc_for_upload(project_oid, uploaded_file)
 
-    if current_app.config['TESTING']:
-        log.warning('NOT streaming to GCS because TESTING=%r',
-                    current_app.config['TESTING'])
-        # Fake a Blob object.
-        blob = type('Blob', (), {'size': file_size})
-    else:
-        bucket = default_storage_backend(project_id)
-        blob = bucket.blob(internal_fname)
-        blob.create_from_file(stream_for_gcs, file_size)
-        # if current_app.config['STORAGE_BACKEND'] == 'gcs':
-        #     blob, storage_backend = stream_to_gcs(
-        #         file_id, file_size, internal_fname, project_id,
-        #         stream_for_gcs, uploaded_file.mimetype)
-        # elif current_app.config['STORAGE_BACKEND'] == 'local':
-        #     storage_backend = LocalBucket(project_id)
-        #     blob = LocalBlob(project_id, internal_fname)
-        #     blob.create_from_file(stream_for_gcs, file_size)
+    # Copy the file into storage.
+    bucket = default_storage_backend(project_id)
+    blob = bucket.blob(internal_fname)
+    blob.create_from_file(stream_for_gcs,
+                          file_size=file_size,
+                          content_type=uploaded_file.mimetype)
 
     log.debug('Marking uploaded file id=%s, fname=%s, '
               'size=%i as "queued_for_processing"',
@@ -708,8 +664,7 @@ def stream_to_storage(project_id):
 
     log.debug('Processing uploaded file id=%s, fname=%s, size=%i', file_id,
               internal_fname, blob.size)
-    # process_file(storage_backend, file_id, local_file)
-    blob.process_file(file_id)
+    process_file(bucket, file_id, local_file)
 
     # Local processing is done, we can close the local file so it is removed.
     if local_file is not None:
@@ -727,20 +682,17 @@ def stream_to_storage(project_id):
     return resp
 
 
-def stream_to_gcs(file_id, file_size, internal_fname, project_id,
-                  stream_for_gcs, content_type):
+from ..file_storage_backends.abstract import FileType
+
+
+def stream_to_gcs(file_id: ObjectId, file_size: int, internal_fname: str, project_id: ObjectId,
+                  stream_for_gcs: FileType, content_type: str) \
+        -> typing.Tuple[GoogleCloudStorageBlob, GoogleCloudStorageBucket]:
     # Upload the file to GCS.
-    from gcloud.streaming import transfer
-    log.debug('Streaming file to GCS bucket; id=%s, fname=%s, size=%i',
-              file_id, internal_fname, file_size)
-    # Files larger than this many bytes will be streamed directly from disk,
-    # smaller ones will be read into memory and then uploaded.
-    transfer.RESUMABLE_UPLOAD_THRESHOLD = 102400
     try:
-        gcs = GoogleCloudStorageBucket(project_id)
-        file_in_storage = GoogleCloudStorageBlob(gcs, internal_fname)
-        file_in_storage.blob.upload_from_file(stream_for_gcs, size=file_size,
-                                              content_type=content_type)
+        bucket = GoogleCloudStorageBucket(str(project_id))
+        blob = bucket.blob(internal_fname)
+        blob.create_from_file(stream_for_gcs, file_size=file_size, content_type=content_type)
     except Exception:
         log.exception('Error uploading file to Google Cloud Storage (GCS),'
                       ' aborting handling of uploaded file (id=%s).', file_id)
@@ -748,9 +700,7 @@ def stream_to_gcs(file_id, file_size, internal_fname, project_id,
         raise wz_exceptions.InternalServerError(
             'Unable to stream file to Google Cloud Storage')
 
-    # Reload the blob to get the file size according to Google.
-    file_in_storage.blob.reload()
-    return file_in_storage, gcs
+    return blob, bucket
 
 
 def add_access_control_headers(resp):
@@ -841,8 +791,6 @@ def setup_app(app, url_prefix):
     app.on_fetched_item_files += before_returning_file
     app.on_fetched_resource_files += before_returning_files
 
-    app.on_delete_item_files += before_deleting_file
-
     app.on_update_files += compute_aggregate_length
     app.on_replace_files += compute_aggregate_length
     app.on_insert_files += compute_aggregate_length_items
diff --git a/pillar/api/file_storage/moving.py b/pillar/api/file_storage/moving.py
index 592be437..5c37831a 100644
--- a/pillar/api/file_storage/moving.py
+++ b/pillar/api/file_storage/moving.py
@@ -5,14 +5,13 @@ import logging
 import os
 import tempfile
 
-from bson import ObjectId
 import bson.tz_util
-from flask import current_app
 import requests
 import requests.exceptions
+from bson import ObjectId
+from flask import current_app
 
 from . import stream_to_gcs, generate_all_links, ensure_valid_link
-import pillar.api.utils.gcs
 
 __all__ = ['PrerequisiteNotMetError', 'change_file_storage_backend']
 
@@ -90,22 +89,23 @@ def copy_file_to_backend(file_id, project_id, file_or_var, src_backend, dest_bac
     else:
         local_finfo = fetch_file_from_link(file_or_var['link'])
 
-    # Upload to GCS
-    if dest_backend != 'gcs':
-        raise ValueError('Only dest_backend="gcs" is supported now.')
+    try:
+        # Upload to GCS
+        if dest_backend != 'gcs':
+            raise ValueError('Only dest_backend="gcs" is supported now.')
 
-    if current_app.config['TESTING']:
-        log.warning('Skipping actual upload to GCS due to TESTING')
-    else:
-        # TODO check for name collisions
-        stream_to_gcs(file_id, local_finfo['file_size'],
-                      internal_fname=internal_fname,
-                      project_id=str(project_id),
-                      stream_for_gcs=local_finfo['local_file'],
-                      content_type=local_finfo['content_type'])
-
-    # No longer needed, so it can be closed & dispersed of.
-    local_finfo['local_file'].close()
+        if current_app.config['TESTING']:
+            log.warning('Skipping actual upload to GCS due to TESTING')
+        else:
+            # TODO check for name collisions
+            stream_to_gcs(file_id, local_finfo['file_size'],
+                          internal_fname=internal_fname,
+                          project_id=project_id,
+                          stream_for_gcs=local_finfo['local_file'],
+                          content_type=local_finfo['content_type'])
+    finally:
+        # No longer needed, so it can be closed & dispersed of.
+        local_finfo['local_file'].close()
 
 
 def fetch_file_from_link(link):
@@ -169,10 +169,12 @@ def gcs_move_to_bucket(file_id, dest_project_id, skip_gcs=False):
     if skip_gcs:
         log.warning('NOT ACTUALLY MOVING file %s on GCS, just updating MongoDB', file_id)
     else:
+        from pillar.api.file_storage_backends.gcs import GoogleCloudStorageBucket
+
         src_project = f['project']
-        pillar.api.utils.gcs.copy_to_bucket(f['file_path'], src_project, dest_project_id)
+        GoogleCloudStorageBucket.copy_to_bucket(f['file_path'], src_project, dest_project_id)
         for var in f.get('variations', []):
-            pillar.api.utils.gcs.copy_to_bucket(var['file_path'], src_project, dest_project_id)
+            GoogleCloudStorageBucket.copy_to_bucket(var['file_path'], src_project, dest_project_id)
 
     # Update the file document after moving was successful.
     log.info('Switching file %s to project %s', file_id, dest_project_id)
diff --git a/pillar/api/file_storage_backends/__init__.py b/pillar/api/file_storage_backends/__init__.py
new file mode 100644
index 00000000..3387bd9c
--- /dev/null
+++ b/pillar/api/file_storage_backends/__init__.py
@@ -0,0 +1,25 @@
+"""Storage backends.
+
+To obtain a storage backend, use either of the two forms:
+
+>>> bucket = default_storage_backend('bucket_name')
+
+>>> BucketClass = Bucket.for_backend('backend_name')
+>>> bucket = BucketClass('bucket_name')
+
+"""
+
+from .abstract import Bucket
+
+# Import the other backends so that they register.
+from . import local
+from . import gcs
+
+
+def default_storage_backend(name: str) -> Bucket:
+    from flask import current_app
+
+    backend_name = current_app.config['STORAGE_BACKEND']
+    backend_cls = Bucket.for_backend(backend_name)
+
+    return backend_cls(name)
diff --git a/pillar/api/file_storage_backends/abstract.py b/pillar/api/file_storage_backends/abstract.py
new file mode 100644
index 00000000..1195de71
--- /dev/null
+++ b/pillar/api/file_storage_backends/abstract.py
@@ -0,0 +1,152 @@
+import abc
+import io
+import logging
+import typing
+
+import pathlib
+from bson import ObjectId
+
+__all__ = ['Bucket', 'Blob', 'Path', 'FileType']
+
+# Shorthand for the type of path we use.
+Path = pathlib.PurePosixPath
+
+# This is a mess: typing.IO keeps mypy-0.501 happy, and io.FileIO keeps PyCharm-2017.1 happy.
+FileType = typing.Union[typing.IO, io.FileIO]
+
+
+class Bucket(metaclass=abc.ABCMeta):
+    """Can be a GCS bucket or simply a project folder in Pillar
+
+    :type name: string
+    :param name: Name of the bucket. As a convention, we use the ID of
+    the project to name the bucket.
+
+    """
+
+    # Mapping from backend name to Bucket class
+    backends: typing.Dict[str, typing.Type['Bucket']] = {}
+
+    backend_name: str = None  # define in subclass.
+
+    def __init__(self, name: str) -> None:
+        self.name = name
+
+    def __init_subclass__(cls):
+        assert cls.backend_name, '%s.backend_name must be non-empty string' % cls
+        cls.backends[cls.backend_name] = cls
+
+    def __repr__(self):
+        return f'<{self.__class__.__name__} name={self.name!r}>'
+
+    @classmethod
+    def for_backend(cls, backend_name: str) -> typing.Type['Bucket']:
+        """Returns the Bucket subclass for the given backend."""
+        return cls.backends[backend_name]
+
+    @abc.abstractmethod
+    def blob(self, blob_name: str) -> 'Blob':
+        """Factory constructor for blob object.
+
+        :param blob_name: The path of the blob to be instantiated.
+        """
+
+    @abc.abstractmethod
+    def get_blob(self, blob_name: str) -> typing.Optional['Blob']:
+        """Get a blob object by name.
+
+        If the blob exists return the object, otherwise None.
+        """
+
+    @abc.abstractmethod
+    def copy_blob(self, blob: 'Blob', to_bucket: 'Bucket'):
+        """Copies a blob from the current bucket to the other bucket.
+        
+        Implementations only need to support copying between buckets of the
+        same storage backend.
+        """
+
+    @classmethod
+    def copy_to_bucket(cls, blob_name, src_project_id: ObjectId, dest_project_id: ObjectId):
+        """Copies a file from one bucket to the other."""
+
+        src_storage = cls(str(src_project_id))
+        dest_storage = cls(str(dest_project_id))
+
+        blob = src_storage.get_blob(blob_name)
+        src_storage.copy_blob(blob, dest_storage)
+
+
+Bu = typing.TypeVar('Bu', bound=Bucket)
+
+
+class Blob(metaclass=abc.ABCMeta):
+    """A wrapper for file or blob objects."""
+
+    def __init__(self, name: str, bucket: Bucket) -> None:
+        self.name = name
+        self.bucket = bucket
+        self._size_in_bytes: typing.Optional[int] = None
+
+        self.filename: str = None
+        """Name of the file for the Content-Disposition header when downloading it."""
+
+        self._log = logging.getLogger(f'{__name__}.Blob')
+
+    def __repr__(self):
+        return f'<{self.__class__.__name__} bucket={self.bucket.name!r} name={self.name!r}>'
+
+    @property
+    def size(self) -> typing.Optional[int]:
+        """Size of the object, in bytes.
+
+        :returns: The size of the blob or ``None`` if the property
+                  is not set locally.
+        """
+
+        size = self._size_in_bytes
+        if size is None:
+            return None
+        return int(size)
+
+    @abc.abstractmethod
+    def create_from_file(self, file_obj: FileType, *,
+                         content_type: str,
+                         file_size: int = -1):
+        """Copies the file object to the storage.
+        
+        :param file_obj: The file object to send to storage.
+        :param content_type: The content type of the file.
+        :param file_size: The size of the file in bytes, or -1 if unknown
+        """
+
+    def upload_from_path(self, path: pathlib.Path, content_type: str):
+        file_size = path.stat().st_size
+
+        with path.open('rb') as infile:
+            self.create_from_file(infile, content_type=content_type,
+                                  file_size=file_size)
+
+    @abc.abstractmethod
+    def update_filename(self, filename: str):
+        """Sets the filename which is used when downloading the file.
+        
+        Not all storage backends support this, and will use the on-disk filename instead.
+        """
+
+    @abc.abstractmethod
+    def get_url(self, *, is_public: bool) -> str:
+        """Returns the URL to access this blob.
+        
+        Note that this may involve API calls to generate a signed URL.
+        """
+
+    @abc.abstractmethod
+    def make_public(self):
+        """Makes the blob publicly available.
+        
+        Only performs an actual action on backends that support temporary links.
+        """
+
+
+Bl = typing.TypeVar('Bl', bound=Blob)
diff --git a/pillar/api/utils/gcs.py b/pillar/api/file_storage_backends/gcs.py
similarity index 53%
rename from pillar/api/utils/gcs.py
rename to pillar/api/file_storage_backends/gcs.py
index b243b713..8e1e2de3 100644
--- a/pillar/api/utils/gcs.py
+++ b/pillar/api/file_storage_backends/gcs.py
@@ -2,24 +2,24 @@ import os
 import time
 import datetime
 import logging
+import typing
 
 from bson import ObjectId
 from gcloud.storage.client import Client
+import gcloud.storage.blob
 from gcloud.exceptions import NotFound
 from flask import current_app, g
 from werkzeug.local import LocalProxy
 
-from pillar.api.utils.storage import Bucket, Blob
+from .abstract import Bucket, Blob, Path, FileType
 
 log = logging.getLogger(__name__)
 
 
-def get_client():
+def get_client() -> Client:
     """Stores the GCS client on the global Flask object.
 
     The GCS client is not user-specific anyway.
-
-    :rtype: Client
     """
 
     _gcs = getattr(g, '_gcs_client', None)
@@ -31,7 +31,7 @@ def get_client():
 # This hides the specifics of how/where we store the GCS client,
 # and allows the rest of the code to use 'gcs' as a simple variable
 # that does the right thing.
-gcs = LocalProxy(get_client)
+gcs: Client = LocalProxy(get_client)
 
 
 class GoogleCloudStorageBucket(Bucket):
@@ -52,8 +52,11 @@ class GoogleCloudStorageBucket(Bucket):
 
     backend_name = 'gcs'
 
-    def __init__(self, name, subdir='_/'):
-        super(GoogleCloudStorageBucket, self).__init__(name=name)
+    def __init__(self, name: str, subdir='_/') -> None:
+        super().__init__(name=name)
+
+        self._log = logging.getLogger(f'{__name__}.GoogleCloudStorageBucket')
+
         try:
             self._gcs_bucket = gcs.get_bucket(name)
         except NotFound:
@@ -73,138 +76,110 @@ class GoogleCloudStorageBucket(Bucket):
 
         self.subdir = subdir
 
-    def blob(self, blob_name):
+    def blob(self, blob_name: str) -> 'GoogleCloudStorageBlob':
         return GoogleCloudStorageBlob(name=blob_name, bucket=self)
 
-    def List(self, path=None):
-        """Display the content of a subdir in the project bucket. If the path
-        points to a file the listing is simply empty.
+    def get_blob(self, internal_fname: str) -> typing.Optional['GoogleCloudStorageBlob']:
+        blob = self.blob(internal_fname)
+        if not blob.gblob.exists():
+            return None
+        return blob
 
-        :type path: string
-        :param path: The relative path to the directory or asset.
-        """
-        if path and not path.endswith('/'):
-            path += '/'
-        prefix = os.path.join(self.subdir, path)
-
-        fields_to_return = 'nextPageToken,items(name,size,contentType),prefixes'
-        req = self._gcs_bucket.list_blobs(fields=fields_to_return, prefix=prefix,
-                                          delimiter='/')
-
-        files = []
-        for f in req:
-            filename = os.path.basename(f.name)
-            if filename != '':  # Skip own folder name
-                files.append(dict(
-                    path=os.path.relpath(f.name, self.subdir),
-                    text=filename,
-                    type=f.content_type))
-
-        directories = []
-        for dir_path in req.prefixes:
-            directory_name = os.path.basename(os.path.normpath(dir_path))
-            directories.append(dict(
-                text=directory_name,
-                path=os.path.relpath(dir_path, self.subdir),
-                type='group_storage',
-                children=True))
-            # print os.path.basename(os.path.normpath(path))
-
-        list_dict = dict(
-            name=os.path.basename(os.path.normpath(path)),
-            type='group_storage',
-            children=files + directories
-        )
-
-        return list_dict
-
-    def blob_to_dict(self, blob):
-        blob.reload()
-        expiration = datetime.datetime.now() + datetime.timedelta(days=1)
-        expiration = int(time.mktime(expiration.timetuple()))
-        return dict(
-            updated=blob.updated,
-            name=os.path.basename(blob.name),
-            size=blob.size,
-            content_type=blob.content_type,
-            signed_url=blob.generate_signed_url(expiration),
-            public_url=blob.public_url)
-
-    def Get(self, path, to_dict=True):
+    def _gcs_get(self, path: str, *, chunk_size=None) -> gcloud.storage.Blob:
         """Get selected file info if the path matches.
 
-        :type path: string
-        :param path: The relative path to the file.
-        :type to_dict: bool
-        :param to_dict: Return the object as a dictionary.
+        :param path: The path to the file, relative to the bucket's subdir.
         """
         path = os.path.join(self.subdir, path)
-        blob = self._gcs_bucket.blob(path)
-        if blob.exists():
-            if to_dict:
-                return self.blob_to_dict(blob)
-            else:
-                return blob
-        else:
-            return None
+        blob = self._gcs_bucket.blob(path, chunk_size=chunk_size)
+        return blob
 
-    def Post(self, full_path, path=None):
+    def _gcs_post(self, full_path, *, path=None) -> typing.Optional[gcloud.storage.Blob]:
         """Create new blob and upload data to it.
         """
         path = path if path else os.path.join('_', os.path.basename(full_path))
-        blob = self._gcs_bucket.blob(path)
-        if blob.exists():
+        gblob = self._gcs_bucket.blob(path)
+        if gblob.exists():
+            self._log.error(f'Trying to upload to {path}, but that blob already exists. '
+                            f'Not uploading.')
             return None
-        blob.upload_from_filename(full_path)
-        return blob
+
+        gblob.upload_from_filename(full_path)
+        return gblob
         # return self.blob_to_dict(blob) # Has issues with threading
 
-    def Delete(self, path):
-        """Delete blob (when removing an asset or replacing a preview)"""
+    def delete_blob(self, path: str) -> bool:
+        """Deletes the blob (when removing an asset or replacing a preview)"""
 
         # We want to get the actual blob to delete
-        blob = self.Get(path, to_dict=False)
+        gblob = self._gcs_get(path)
         try:
-            blob.delete()
+            gblob.delete()
             return True
         except NotFound:
-            return None
+            return False
 
-    def update_name(self, blob, name):
-        """Set the ContentDisposition metadata so that when a file is downloaded
-        it has a human-readable name.
-        """
-        blob.content_disposition = 'attachment; filename="{0}"'.format(name)
-        blob.patch()
-
-    def copy_blob(self, blob, to_bucket):
+    def copy_blob(self, blob: Blob, to_bucket: Bucket):
         """Copies the given blob from this bucket to the other bucket.
 
         Returns the new blob.
         """
 
+        assert isinstance(blob, GoogleCloudStorageBlob)
         assert isinstance(to_bucket, GoogleCloudStorageBucket)
-        return self._gcs_bucket.copy_blob(blob, to_bucket._gcs_bucket)
 
-    def get_blob(self, internal_fname, chunk_size=256 * 1024 * 2):
-        return self._gcs_bucket.blob('_/' + internal_fname, chunk_size)
+        self._log.info('Copying %s to bucket %s', blob, to_bucket)
+
+        return self._gcs_bucket.copy_blob(blob.gblob, to_bucket._gcs_bucket)
 
 
 class GoogleCloudStorageBlob(Blob):
     """GCS blob interface."""
-    def __init__(self, name, bucket):
-        super(GoogleCloudStorageBlob, self).__init__(name, bucket)
 
-        self.blob = bucket.gcs_bucket.blob('_/' + name, chunk_size=256 * 1024 * 2)
+    def __init__(self, name: str, bucket: GoogleCloudStorageBucket) -> None:
+        super().__init__(name, bucket)
 
-    def create_from_file(self, uploaded_file, file_size):
-        raise NotImplementedError()
+        self._log = logging.getLogger(f'{__name__}.GoogleCloudStorageBlob')
+        self.gblob = bucket._gcs_get(name, chunk_size=256 * 1024 * 2)
 
-    def _process_image(self, file_doc):
-        raise NotImplementedError()
+    def create_from_file(self, file_obj: FileType, *,
+                         content_type: str,
+                         file_size: int = -1) -> None:
+        from gcloud.streaming import transfer
 
-    def _process_video(self, file_doc):
-        raise NotImplementedError()
+        self._log.debug('Streaming file to GCS bucket %r, size=%i', self, file_size)
+
+        # Files larger than this many bytes will be streamed directly from disk,
+        # smaller ones will be read into memory and then uploaded.
+        transfer.RESUMABLE_UPLOAD_THRESHOLD = 102400
+        self.gblob.upload_from_file(file_obj,
+                                    size=file_size,
+                                    content_type=content_type)
+
+        # Reload the blob to get the file size according to Google.
+        self.gblob.reload()
+        self._size_in_bytes = self.gblob.size
+
+    def update_filename(self, filename: str):
+        """Set the ContentDisposition metadata so that when a file is downloaded
+        it has a human-readable name.
+        """
+
+        if '"' in filename:
+            raise ValueError(f'Filename is not allowed to have double quote in it: {filename!r}')
+
+        self.gblob.content_disposition = f'attachment; filename="{filename}"'
+        self.gblob.patch()
+
+    def get_url(self, *, is_public: bool) -> str:
+        if is_public:
+            return self.gblob.public_url
+
+        expiration = datetime.datetime.utcnow() + datetime.timedelta(days=1)
+        return self.gblob.generate_signed_url(expiration)
+
+    def make_public(self):
+        self.gblob.make_public()
 
 
 def update_file_name(node):
@@ -233,7 +208,7 @@ def update_file_name(node):
         map_type = file_props.get('map_type', '')
 
         storage = GoogleCloudStorageBucket(str(node['project']))
-        blob = storage.Get(file_doc['file_path'], to_dict=False)
+        blob = storage.get_blob(file_doc['file_path'])
         if blob is None:
             log.warning('Unable to find blob for file %s in project %s',
                         file_doc['file_path'], file_doc['project'])
@@ -242,18 +217,18 @@ def update_file_name(node):
         # Pick file extension from original filename
         _, ext = os.path.splitext(file_doc['filename'])
         name = _format_name(node['name'], ext, map_type=map_type)
-        storage.update_name(blob, name)
+        blob.update_filename(name)
 
         # Assign the same name to variations
         for v in file_doc.get('variations', []):
             _, override_ext = os.path.splitext(v['file_path'])
             name = _format_name(node['name'], override_ext, v['size'], map_type=map_type)
-            blob = storage.Get(v['file_path'], to_dict=False)
+            blob = storage.get_blob(v['file_path'])
             if blob is None:
                 log.info('Unable to find blob for file %s in project %s. This can happen if the '
                          'video encoding is still processing.', v['file_path'], node['project'])
                 continue
-            storage.update_name(blob, name)
+            blob.update_filename(name)
 
     # Currently we search for 'file' and 'files' keys in the object properties.
     # This could become a bit more flexible and realy on a true reference of the
@@ -264,16 +239,3 @@ def update_file_name(node):
     if 'files' in node['properties']:
         for file_props in node['properties']['files']:
             _update_name(file_props['file'], file_props)
-
-
-def copy_to_bucket(file_path, src_project_id, dest_project_id):
-    """Copies a file from one bucket to the other."""
-
-    log.info('Copying %s from project bucket %s to %s',
-             file_path, src_project_id, dest_project_id)
-
-    src_storage = GoogleCloudStorageBucket(str(src_project_id))
-    dest_storage = GoogleCloudStorageBucket(str(dest_project_id))
-
-    blob = src_storage.Get(file_path, to_dict=False)
-    src_storage.copy_blob(blob, dest_storage)
diff --git a/pillar/api/file_storage_backends/local.py b/pillar/api/file_storage_backends/local.py
new file mode 100644
index 00000000..3b2243de
--- /dev/null
+++ b/pillar/api/file_storage_backends/local.py
@@ -0,0 +1,100 @@
+import logging
+import typing
+
+import pathlib
+from flask import current_app
+
+from pillar.api.utils.imaging import generate_local_thumbnails
+
+__all__ = ['LocalBucket', 'LocalBlob']
+
+from .abstract import Bucket, Blob, FileType, Path
+
+
+class LocalBucket(Bucket):
+    backend_name = 'local'
+
+    def __init__(self, name: str) -> None:
+        super().__init__(name)
+
+        self._log = logging.getLogger(f'{__name__}.LocalBucket')
+
+        # For local storage, the name is actually a partial path, relative
+        # to the local storage root.
+        self.root = pathlib.Path(current_app.config['STORAGE_DIR'])
+        self.abspath = self.root / name[:2] / name
+
+    def blob(self, blob_name: str) -> 'LocalBlob':
+        return LocalBlob(name=blob_name, bucket=self)
+
+    def get_blob(self, blob_name: str) -> typing.Optional['LocalBlob']:
+        # TODO: Check if file exists, otherwise None
+        return self.blob(blob_name)
+
+    def copy_blob(self, blob: Blob, to_bucket: Bucket):
+        """Copies a blob from the current bucket to the other bucket.
+        
+        Implementations only need to support copying between buckets of the
+        same storage backend.
+        """
+
+        assert isinstance(blob, LocalBlob)
+        assert isinstance(to_bucket, LocalBucket)
+
+        self._log.info('Copying %s to bucket %s', blob, to_bucket)
+
+        dest_blob = to_bucket.blob(blob.name)
+
+        # TODO: implement content type handling for local storage.
+        self._log.warning('Unable to set correct file content type for %s', dest_blob)
+
+        with open(blob.abspath(), 'rb') as src_file:
+            dest_blob.create_from_file(src_file, content_type='application/x-octet-stream')
+
+
+class LocalBlob(Blob):
+    """Blob representing a local file on the filesystem."""
+
+    bucket: LocalBucket
+
+    def __init__(self, name: str, bucket: LocalBucket) -> None:
+        super().__init__(name, bucket)
+
+        self._log = logging.getLogger(f'{__name__}.LocalBlob')
+        self.partial_path = Path(name[:2]) / name
+
+    def abspath(self) -> pathlib.Path:
+        """Returns a concrete, absolute path to the local file."""
+
+        return pathlib.Path(self.bucket.abspath / self.partial_path)
+
+    def get_url(self, *, is_public: bool) -> str:
+        from flask import url_for
+
+        url = url_for('file_storage.index', file_name=str(self.partial_path), _external=True,
+                      _scheme=current_app.config['SCHEME'])
+        return url
+
+    def create_from_file(self, file_obj: FileType, *,
+                         content_type: str,
+                         file_size: int = -1):
+        assert hasattr(file_obj, 'read')
+
+        import shutil
+
+        # Ensure path exists before saving
+        my_path = self.abspath()
+        my_path.parent.mkdir(exist_ok=True, parents=True)
+
+        with my_path.open('wb') as outfile:
+            shutil.copyfileobj(typing.cast(typing.IO, file_obj), outfile)
+
+        self._size_in_bytes = file_size
+
+    def update_filename(self, filename: str):
+        # TODO: implement this for local storage.
+        self._log.info('update_filename(%r) not supported', filename)
+
+    def make_public(self):
+        # No-op on this storage backend.
+        pass
diff --git a/pillar/api/nodes/__init__.py b/pillar/api/nodes/__init__.py
index f2e65db6..79a3aa30 100644
--- a/pillar/api/nodes/__init__.py
+++ b/pillar/api/nodes/__init__.py
@@ -9,13 +9,13 @@ from bson import ObjectId
 from flask import current_app, g, Blueprint, request
 
 import pillar.markdown
-from pillar.api.node_types import PILLAR_NAMED_NODE_TYPES
 from pillar.api.activities import activity_subscribe, activity_object_add
+from pillar.api.node_types import PILLAR_NAMED_NODE_TYPES
+from pillar.api.file_storage_backends.gcs import update_file_name
+from pillar.api.utils import str2id, jsonify
 from pillar.api.utils.algolia import algolia_index_node_delete
 from pillar.api.utils.algolia import algolia_index_node_save
-from pillar.api.utils import str2id, jsonify
 from pillar.api.utils.authorization import check_permissions, require_login
-from pillar.api.utils.gcs import update_file_name
 
 log = logging.getLogger(__name__)
 blueprint = Blueprint('nodes_api', __name__)
diff --git a/pillar/api/projects/hooks.py b/pillar/api/projects/hooks.py
index 4a4bdcf1..3464d606 100644
--- a/pillar/api/projects/hooks.py
+++ b/pillar/api/projects/hooks.py
@@ -3,12 +3,13 @@ import logging
 
 from flask import request, abort, current_app
 from gcloud import exceptions as gcs_exceptions
+
 from pillar.api.node_types.asset import node_type_asset
 from pillar.api.node_types.comment import node_type_comment
 from pillar.api.node_types.group import node_type_group
 from pillar.api.node_types.group_texture import node_type_group_texture
 from pillar.api.node_types.texture import node_type_texture
-from pillar.api.utils.gcs import GoogleCloudStorageBucket
+from pillar.api.file_storage_backends.gcs import GoogleCloudStorageBucket
 from pillar.api.utils import authorization, authentication
 from pillar.api.utils import remove_private_keys
 from pillar.api.utils.authorization import user_has_role, check_permissions
diff --git a/pillar/api/utils/imaging.py b/pillar/api/utils/imaging.py
index af92480a..83883142 100644
--- a/pillar/api/utils/imaging.py
+++ b/pillar/api/utils/imaging.py
@@ -5,6 +5,7 @@ from PIL import Image
 from flask import current_app
 
 
+# TODO: refactor to use pathlib.Path and f-strings.
 def generate_local_thumbnails(name_base, src):
     """Given a source image, use Pillow to generate thumbnails according to the
     application settings.
diff --git a/pillar/api/utils/storage.py b/pillar/api/utils/storage.py
index aaae96ae..e0a8855a 100644
--- a/pillar/api/utils/storage.py
+++ b/pillar/api/utils/storage.py
@@ -1,266 +1 @@
 """Utility for managing storage backends and files."""
-
-import abc
-import logging
-import os
-import shutil
-import typing
-
-from bson import ObjectId
-from flask import current_app
-
-from pillar.api import utils
-from pillar.api.utils.authorization import user_has_role
-from pillar.api.utils.imaging import generate_local_thumbnails
-
-log = logging.getLogger(__name__)
-
-
-class Bucket(metaclass=abc.ABCMeta):
-    """Can be a GCS bucket or simply a project folder in Pillar
-
-    :type name: string
-    :param name: Name of the bucket. As a convention, we use the ID of
-    the project to name the bucket.
-
-    """
-
-    # Mapping from backend name to Bucket class
-    backends = {}
-
-    backend_name: str = None  # define in subclass.
-
-    def __init__(self, name):
-        self.name = name
-
-    def __init_subclass__(cls, **kwargs):
-        super().__init_subclass__(**kwargs)
-        assert cls.backend_name, '%s.backend_name must be non-empty string' % cls
-        cls.backends[cls.backend_name] = cls
-
-    @classmethod
-    def for_backend(cls, backend_name: str) -> type:
-        """Returns the Bucket subclass for the given backend."""
-        return cls.backends[backend_name]
-
-    @abc.abstractmethod
-    def blob(self, blob_name) -> 'Blob':
-        """Factory constructor for blob object.
-
-        :type blob_name: string
-        :param blob_name: The name of the blob to be instantiated.
-        """
-        return Blob(name=blob_name, bucket=self)
-
-    @abc.abstractmethod
-    def get_blob(self, blob_name) -> typing.Optional['Blob']:
-        """Get a blob object by name.
-
-        If the blob exists return the object, otherwise None.
-        """
-        pass
-
-
-class Blob(metaclass=abc.ABCMeta):
-    """A wrapper for file or blob objects.
-
-    :type name: string
-    :param name: Name of the blob.
-
-    """
-
-    def __init__(self, name: str, bucket: Bucket):
-        self.name = name
-        self.bucket = bucket
-        self._size_in_bytes = None
-
-    @property
-    def size(self) -> typing.Optional[int]:
-        """Size of the object, in bytes.
-
-        :returns: The size of the blob or ``None`` if the property
-                  is not set locally.
-        """
-        size = self._size_in_bytes
-        if size is not None:
-            return int(size)
-        return self._size_in_bytes
-
-    @abc.abstractmethod
-    def create_from_file(self, uploaded_file, file_size):
-        pass
-
-    @abc.abstractmethod
-    def _process_image(self, file_doc):
-        pass
-
-    @abc.abstractmethod
-    def _process_video(self, file_doc):
-        pass
-
-    # TODO Sybren: change file_id type to ObjectId?
-    def process_file(self, file_id: str):
-        """Generate image thumbnails or encode video.
-
-        :type file_id: string
-        :param file_id: The document ID for the file processed. We need it to
-        update the document as we process the file.
-        """
-
-        def update_file_doc(file_id, **updates):
-            res = files.update_one({'_id': ObjectId(file_id)},
-                                   {'$set': updates})
-
-            log.debug('update_file_doc(%s, %s): %i matched, %i updated.',
-                      file_id, updates, res.matched_count, res.modified_count)
-            return res
-
-        file_id = ObjectId(file_id)
-
-        # Fetch the src_file document from MongoDB.
-        files = current_app.data.driver.db['files']
-        src_file = files.find_one(file_id)
-        if not src_file:
-            log.warning(
-                'process_file(%s): no such file document found, ignoring.')
-            return
-
-        # Update the 'format' field from the content type.
-        # TODO: overrule the content type based on file extention & magic numbers.
-        mime_category, src_file['format'] = src_file['content_type'].split('/', 1)
-
-        # Prevent video handling for non-admins.
-        if not user_has_role('admin') and mime_category == 'video':
-            if src_file['format'].startswith('x-'):
-                xified = src_file['format']
-            else:
-                xified = 'x-' + src_file['format']
-
-            src_file['content_type'] = 'application/%s' % xified
-            mime_category = 'application'
-            log.info('Not processing video file %s for non-admin user', file_id)
-
-        # Run the required processor, based on the MIME category.
-        processors = {
-            'image': self._process_image,
-            'video': self._process_video,
-        }
-
-        try:
-            processor = processors[mime_category]
-        except KeyError:
-            log.info("POSTed file %s was of type %r, which isn't "
-                     "thumbnailed/encoded.", file_id,
-                     mime_category)
-            src_file['status'] = 'complete'
-        else:
-            log.debug('process_file(%s): marking file status as "processing"',
-                      file_id)
-            src_file['status'] = 'processing'
-            update_file_doc(file_id, status='processing')
-
-            try:
-                processor(src_file)
-            except Exception:
-                log.warning('process_file(%s): error when processing file, '
-                            'resetting status to '
-                            '"queued_for_processing"', file_id, exc_info=True)
-                update_file_doc(file_id, status='queued_for_processing')
-                return
-
-        src_file = utils.remove_private_keys(src_file)
-        # Update the original file with additional info, e.g. image resolution
-        r, _, _, status = current_app.put_internal('files', src_file,
-                                                   _id=file_id)
-        if status not in (200, 201):
-            log.warning(
-                'process_file(%s): status %i when saving processed file '
-                'info to MongoDB: %s',
-                file_id, status, r)
-
-
-class LocalBucket(Bucket):
-    backend_name = 'local'
-
-    def blob(self, blob_name: str) -> 'LocalBlob':
-        return LocalBlob(name=blob_name, bucket=self)
-
-    def get_blob(self, blob_name: str) -> typing.Optional['LocalBlob']:
-        # TODO: Check if file exists, otherwise None
-        return self.blob(blob_name)
-
-
-class LocalBlob(Blob):
-    def __init__(self, name: str, bucket: LocalBucket):
-        super().__init__(name=name, bucket=bucket)
-
-        bucket_name = bucket.name
-        self.partial_path = os.path.join(bucket_name[:2], bucket_name,
-                                         name[:2], name)
-        self.path = os.path.join(
-            current_app.config['STORAGE_DIR'], self.partial_path)
-
-    def create_from_file(self, uploaded_file: typing.io.BinaryIO, file_size: int):
-        assert hasattr(uploaded_file, 'read')
-
-        # Ensure path exists before saving
-        directory = os.path.dirname(self.path)
-        if not os.path.exists(directory):
-            os.makedirs(directory)
-
-        with open(self.path, 'wb') as outfile:
-            shutil.copyfileobj(uploaded_file, outfile)
-
-        self._size_in_bytes = file_size
-
-    def _process_image(self, file_doc: dict):
-        from PIL import Image
-
-        im = Image.open(self.path)
-        res = im.size
-        file_doc['width'] = res[0]
-        file_doc['height'] = res[1]
-
-        # Generate previews
-        log.info('Generating thumbnails for file %s', file_doc['_id'])
-        file_doc['variations'] = generate_local_thumbnails(file_doc['name'],
-                                                           self.path)
-
-        # Send those previews to Google Cloud Storage.
-        log.info('Uploading %i thumbnails for file %s to Google Cloud Storage '
-                 '(GCS)', len(file_doc['variations']), file_doc['_id'])
-
-        # TODO: parallelize this at some point.
-        for variation in file_doc['variations']:
-            fname = variation['file_path']
-            if current_app.config['TESTING']:
-                log.warning('  - NOT making thumbnails', fname)
-            else:
-                log.debug('  - Sending thumbnail %s to %s', fname, self.bucket)
-
-                blob = self.bucket.blob(fname)
-                with open(variation['local_path'], 'rb') as local_file:
-                    blob.create_from_file(local_file, variation['length'])
-
-            try:
-                os.unlink(variation['local_path'])
-            except OSError:
-                log.warning(
-                    'Unable to unlink %s, ignoring this but it will need '
-                    'cleanup later.', variation['local_path'])
-
-            del variation['local_path']
-
-        log.info('Done processing file %s', file_doc['_id'])
-        file_doc['status'] = 'complete'
-
-    def _process_video(self, file_doc):
-        pass
-
-
-def default_storage_backend(name):
-    from flask import current_app
-
-    backend_name = current_app.config['STORAGE_BACKEND']
-    backend_cls = Bucket.for_backend(backend_name)
-    return backend_cls(name)
diff --git a/pillar/tests/__init__.py b/pillar/tests/__init__.py
index 704f62bc..1c44164b 100644
--- a/pillar/tests/__init__.py
+++ b/pillar/tests/__init__.py
@@ -29,15 +29,6 @@ import responses
 import pillar
 from . import common_test_data as ctd
 
-# from six:
-PY3 = sys.version_info[0] == 3
-if PY3:
-    string_type = str
-    text_type = str
-else:
-    string_type = basestring
-    text_type = unicode
-
 MY_PATH = os.path.dirname(os.path.abspath(__file__))
 
 TEST_EMAIL_USER = 'koro'
@@ -71,6 +62,32 @@ class PillarTestServer(pillar.PillarServer):
 class AbstractPillarTest(TestMinimal):
     pillar_server_class = PillarTestServer
 
+    @classmethod
+    def setUpClass(cls):
+        import tempfile
+
+        # Store the global temporary directory location, as Pillar itself will
+        # change this into the config['STORAGE_DIR'] directory. If we don't
+        # restore that, mkdtemp() will keep trying to create inside its previously
+        # created temporary storage directory.
+        cls._orig_tempdir = tempfile.gettempdir()
+
+        # Point the storage directory to something temporary.
+        try:
+            cls._pillar_storage_dir = tempfile.mkdtemp(prefix='test-pillar-storage-')
+        except FileNotFoundError as ex:
+            raise FileNotFoundError(f'Error creating temp dir: {ex}')
+        os.environ['PILLAR_STORAGE_DIR'] = cls._pillar_storage_dir
+
+    @classmethod
+    def tearDownClass(cls):
+        import tempfile
+        import shutil
+
+        tempfile.tempdir = cls._orig_tempdir
+        shutil.rmtree(cls._pillar_storage_dir)
+
+
     def setUp(self, **kwargs):
         eve_settings_file = os.path.join(MY_PATH, 'eve_test_settings.py')
         kwargs['settings_file'] = eve_settings_file
@@ -81,6 +98,8 @@ class AbstractPillarTest(TestMinimal):
         config.DEBUG = True
 
         self.app = self.pillar_server_class(os.path.dirname(os.path.dirname(__file__)))
+        self.assertEqual(self.app.config['STORAGE_DIR'], self._pillar_storage_dir)
+
         self.app.process_extensions()
         assert self.app.config['MONGO_DBNAME'] == 'pillar_test'
 
@@ -301,7 +320,7 @@ class AbstractPillarTest(TestMinimal):
                       json=BLENDER_ID_USER_RESPONSE,
                       status=200)
 
-    def make_header(self, username: str, subclient_id: str='') -> bytes:
+    def make_header(self, username: str, subclient_id: str = '') -> bytes:
         """Returns a Basic HTTP Authentication header value."""
 
         content = '%s:%s' % (username, subclient_id)
@@ -348,16 +367,16 @@ class AbstractPillarTest(TestMinimal):
         if not isinstance(params, dict):
             return params
 
-        def convert_to_string(param):
+        def convert_to_bytes(param):
             if isinstance(param, dict):
                 return json.dumps(param, sort_keys=True)
-            if isinstance(param, text_type):
+            if isinstance(param, str):
                 return param.encode('utf-8')
             return param
 
         # Pass as (key, value) pairs, so that the sorted order is maintained.
         jsonified_params = [
-            (key, convert_to_string(params[key]))
+            (key, convert_to_bytes(params[key]))
             for key in sorted(params.keys())]
         return urlencode(jsonified_params)
 
diff --git a/pillar/tests/config_testing.py b/pillar/tests/config_testing.py
index f56facac..b27fcb1f 100644
--- a/pillar/tests/config_testing.py
+++ b/pillar/tests/config_testing.py
@@ -9,3 +9,6 @@ CDN_STORAGE_USER = 'u41508580125621'
 
 FILESIZE_LIMIT_BYTES_NONSUBS = 20 * 2 ** 10
 ROLES_FOR_UNLIMITED_UPLOADS = {'subscriber', 'demo', 'admin'}
+
+GCLOUD_APP_CREDENTIALS = 'invalid-file-because-gcloud-storage-should-be-mocked-in-tests'
+STORAGE_BACKEND = 'local'
diff --git a/requirements-dev.txt b/requirements-dev.txt
index f628b3fa..bf184130 100644
--- a/requirements-dev.txt
+++ b/requirements-dev.txt
@@ -8,6 +8,8 @@ responses==0.5.1
 pytest-cov==2.4.0
 mock==2.0.0
 
+# mypy-0.501 typed-ast-1.0.2
+
 # Secondary development requirements
 cookies==2.2.1
 coverage==4.3.4
diff --git a/setup.cfg b/setup.cfg
index 3c19782f..ebdcd747 100644
--- a/setup.cfg
+++ b/setup.cfg
@@ -1,5 +1,11 @@
 [tool:pytest]
-addopts = -v --cov pillar --cov-report term-missing --ignore node_modules -x
+addopts = -v --cov pillar --cov-report term-missing --ignore node_modules
+
+[mypy]
+python_version = 3.6
+warn_unused_ignores = True
+ignore_missing_imports = True
+follow_imports = skip
 
 [pep8]
 max-line-length = 100