diff --git a/data/model/storage.py b/data/model/storage.py
index d3e452d9f..ef983ecc9 100644
--- a/data/model/storage.py
+++ b/data/model/storage.py
@@ -1,6 +1,6 @@
 import logging
 
-from peewee import JOIN_LEFT_OUTER, fn
+from peewee import JOIN_LEFT_OUTER, fn, SQL
 
 from data.model import config, db_transaction, InvalidImageException
 from data.database import (ImageStorage, Image, DerivedImageStorage, ImageStoragePlacement,
@@ -218,13 +218,26 @@ def get_layer_path(storage_record):
 
   return store.blob_path(storage_record.content_checksum)
 
+
 def lookup_repo_storages_by_content_checksum(repo, checksums):
   """ Looks up repository storages (without placements) matching the given repository
       and checksum. """
-  return (ImageStorage
-          .select()
-          .join(Image)
-          .where(Image.repository == repo, ImageStorage.content_checksum << checksums))
+  # There may be many duplicates of the checksums, so for performance reasons we are going
+  # to use a union to select just one storage with each checksum
+  queries = []
+
+  for checksum in set(checksums):
+    candidate_subq = (ImageStorage
+                      .select(ImageStorage.id, ImageStorage.content_checksum)
+                      .join(Image)
+                      .where(Image.repository == repo, ImageStorage.content_checksum == checksum)
+                      .limit(1))
+    queries.append(ImageStorage
+                   .select(SQL('*'))
+                   .from_(candidate_subq))
+
+  return reduce(lambda l, r: l.union_all(r), queries)
+
 
 def get_storage_locations(uuid):
   query = (ImageStoragePlacement
diff --git a/data/model/tag.py b/data/model/tag.py
index 6883a39e3..96b3ffef4 100644
--- a/data/model/tag.py
+++ b/data/model/tag.py
@@ -240,10 +240,10 @@ def load_manifest_by_digest(namespace, repo_name, digest):
 
 
 def _load_repo_manifests(namespace, repo_name):
-    return (TagManifest
-            .select(TagManifest, RepositoryTag)
-            .join(RepositoryTag)
-            .join(Image)
-            .join(Repository)
-            .join(Namespace, on=(Namespace.id == Repository.namespace_user))
-            .where(Repository.name == repo_name, Namespace.username == namespace))
+    return _tag_alive(TagManifest
+                      .select(TagManifest, RepositoryTag)
+                      .join(RepositoryTag)
+                      .join(Image)
+                      .join(Repository)
+                      .join(Namespace, on=(Namespace.id == Repository.namespace_user))
+                      .where(Repository.name == repo_name, Namespace.username == namespace))
diff --git a/endpoints/v2/manifest.py b/endpoints/v2/manifest.py
index 935045734..1ba9be99f 100644
--- a/endpoints/v2/manifest.py
+++ b/endpoints/v2/manifest.py
@@ -287,16 +287,16 @@ def _write_manifest(namespace, repo_name, manifest):
   # know which V1 images we need to synthesize and which ones are invalid.
   layers = list(manifest.layers)
 
-  docker_image_ids = [mdata.v1_metadata.docker_id for mdata in layers]
-  parent_image_ids = [mdata.v1_metadata.parent for mdata in layers
-                      if mdata.v1_metadata.parent]
-  all_image_ids = list(set(docker_image_ids + parent_image_ids))
+  docker_image_ids = {mdata.v1_metadata.docker_id for mdata in layers}
+  parent_image_ids = {mdata.v1_metadata.parent for mdata in layers
+                      if mdata.v1_metadata.parent}
+  all_image_ids = list(docker_image_ids | parent_image_ids)
 
   images_query = model.image.lookup_repository_images(repo, all_image_ids)
   images_map = {image.docker_image_id: image for image in images_query}
 
   # Lookup the storages associated with each blob in the manifest.
-  checksums = [str(mdata.digest) for mdata in manifest.layers]
+  checksums = list({str(mdata.digest) for mdata in manifest.layers})
   storage_query = model.storage.lookup_repo_storages_by_content_checksum(repo, checksums)
   storage_map = {storage.content_checksum: storage for storage in storage_query}