diff --git a/marconi/storage/mongodb/claims.py b/marconi/storage/mongodb/claims.py
index ec7e98f1e..4771ac805 100644
--- a/marconi/storage/mongodb/claims.py
+++ b/marconi/storage/mongodb/claims.py
@@ -66,11 +66,9 @@ class ClaimController(storage.ClaimBase):
 
         # Base query, always check expire time
         now = timeutils.utcnow()
-
-        try:
-            cid = utils.to_oid(claim_id)
-        except ValueError:
-            raise exceptions.ClaimDoesNotExist()
+        cid = utils.to_oid(claim_id)
+        if cid is None:
+            raise exceptions.ClaimDoesNotExist(queue, project, claim_id)
 
         def messages(msg_iter):
             msg = next(msg_iter)
@@ -188,9 +186,8 @@ class ClaimController(storage.ClaimBase):
 
     @utils.raises_conn_error
     def update(self, queue, claim_id, metadata, project=None):
-        try:
-            cid = utils.to_oid(claim_id)
-        except ValueError:
+        cid = utils.to_oid(claim_id)
+        if cid is None:
             raise exceptions.ClaimDoesNotExist(claim_id, queue, project)
 
         now = timeutils.utcnow()
diff --git a/marconi/storage/mongodb/messages.py b/marconi/storage/mongodb/messages.py
index 9ca03dfb3..ef85145dc 100644
--- a/marconi/storage/mongodb/messages.py
+++ b/marconi/storage/mongodb/messages.py
@@ -368,9 +368,11 @@ class MessageController(storage.MessageBase):
         return utils.HookedCursor(msgs, denormalizer)
 
     def unclaim(self, queue_name, claim_id, project=None):
-        try:
-            cid = utils.to_oid(claim_id)
-        except ValueError:
+        cid = utils.to_oid(claim_id)
+
+        # NOTE(cpp-cabrera): early abort - avoid a DB query if we're handling
+        # an invalid ID
+        if cid is None:
             return
 
         # NOTE(cpp-cabrera):  unclaim by setting the claim ID to None
@@ -435,7 +437,15 @@ class MessageController(storage.MessageBase):
 
     @utils.raises_conn_error
     def get(self, queue_name, message_id, project=None):
+        """Gets a single message by ID.
+
+        :raises: exceptions.MessageDoesNotExist
+        """
         mid = utils.to_oid(message_id)
+        if mid is None:
+            raise exceptions.MessageDoesNotExist(message_id, queue_name,
+                                                 project)
+
         now = timeutils.utcnow()
 
         query = {
@@ -455,7 +465,10 @@ class MessageController(storage.MessageBase):
 
     @utils.raises_conn_error
     def bulk_get(self, queue_name, message_ids, project=None):
-        message_ids = [utils.to_oid(id) for id in message_ids]
+        message_ids = [mid for mid in map(utils.to_oid, message_ids) if mid]
+        if not message_ids:
+            return ()
+
         now = timeutils.utcnow()
 
         # Base query, always check expire time
@@ -597,50 +610,52 @@ class MessageController(storage.MessageBase):
 
     @utils.raises_conn_error
     def delete(self, queue_name, message_id, project=None, claim=None):
-        try:
-            mid = utils.to_oid(message_id)
+        # NOTE(cpp-cabrera): return early - this is an invalid message
+        # id so we won't be able to find it any way
+        mid = utils.to_oid(message_id)
+        if mid is None:
+            return
 
-            query = {
-                'q': queue_name,
-                'p': project,
-                '_id': mid
-            }
+        query = {
+            'q': queue_name,
+            'p': project,
+            '_id': mid
+        }
 
-            if claim:
-                now = timeutils.utcnow()
-                query['e'] = {'$gt': now}
-                message = self._col.find_one(query)
+        if claim:
+            # NOTE(cpp-cabrera): return early - the user gaves us an
+            # invalid claim id and that renders the rest of this
+            # request moot
+            cid = utils.to_oid(claim)
+            if cid is None:
+                return
 
-                if message is None:
-                    return
+            now = timeutils.utcnow()
+            query['e'] = {'$gt': now}
+            message = self._col.find_one(query)
 
-                cid = utils.to_oid(claim)
+            if message is None:
+                return None
 
-                if not ('c' in message and
-                        message['c']['id'] == cid and
-                        message['c']['e'] > now):
-                    raise exceptions.ClaimNotPermitted(message_id, claim)
+            if not ('c' in message and
+                    message['c']['id'] == cid and
+                    message['c']['e'] > now):
+                raise exceptions.ClaimNotPermitted(message_id, claim)
 
-                self._col.remove(query['_id'], w=0)
-            else:
-                self._col.remove(query, w=0)
-        except exceptions.QueueDoesNotExist:
-            pass
+            self._col.remove(query['_id'], w=0)
+        else:
+            self._col.remove(query, w=0)
 
     @utils.raises_conn_error
     def bulk_delete(self, queue_name, message_ids, project=None):
-        try:
-            message_ids = [utils.to_oid(id) for id in message_ids]
-            query = {
-                'q': queue_name,
-                'p': project,
-                '_id': {'$in': message_ids},
-            }
+        message_ids = [mid for mid in map(utils.to_oid, message_ids) if mid]
+        query = {
+            'q': queue_name,
+            'p': project,
+            '_id': {'$in': message_ids},
+        }
 
-            self._col.remove(query, w=0)
-
-        except exceptions.QueueDoesNotExist:
-            pass
+        self._col.remove(query, w=0)
 
 
 def _basic_message(msg, now):
diff --git a/marconi/storage/mongodb/utils.py b/marconi/storage/mongodb/utils.py
index 0e011527d..f2b59c247 100644
--- a/marconi/storage/mongodb/utils.py
+++ b/marconi/storage/mongodb/utils.py
@@ -117,23 +117,22 @@ def calculate_backoff(attempt, max_attempts, max_sleep, max_jitter=0):
 def to_oid(obj):
     """Creates a new ObjectId based on the input.
 
-    Raises MalformedID when TypeError or berrors.InvalidId
+    Returns None when TypeError or berrors.InvalidId
     is raised by the ObjectID class.
 
     :param obj: Anything that can be passed as an
         input to `objectid.ObjectId`
-
-    :raises: MalformedID
     """
     try:
         return objectid.ObjectId(obj)
     except (TypeError, berrors.InvalidId):
-        msg = u'Invalid oid: %s' % obj
-        raise storage_exceptions.MalformedID(msg)
+        return None
 
 
 def oid_utc(oid):
-    """Converts an ObjectId to a non-tz-aware datetime."""
+    """Converts an ObjectId to a non-tz-aware datetime.
+    :raises: TypeError if oid isn't an ObjectId
+    """
     try:
         return timeutils.normalize_time(oid.generation_time)
     except AttributeError:
diff --git a/marconi/storage/sqlite/claims.py b/marconi/storage/sqlite/claims.py
index 69a258691..4af19dacd 100644
--- a/marconi/storage/sqlite/claims.py
+++ b/marconi/storage/sqlite/claims.py
@@ -47,6 +47,10 @@ class ClaimController(base.ClaimBase):
         if project is None:
             project = ''
 
+        cid = utils.cid_decode(claim_id)
+        if cid is None:
+            raise exceptions.ClaimDoesNotExist(claim_id, queue, project)
+
         with self.driver('deferred'):
             try:
                 id, ttl, age = self.driver.get('''
@@ -55,7 +59,7 @@ class ClaimController(base.ClaimBase):
                         on Q.id = C.qid
                      where C.ttl > julianday() * 86400.0 - C.created
                        and C.id = ? and project = ? and name = ?
-                ''', utils.cid_decode(claim_id), project, queue)
+                ''', cid, project, queue)
 
                 return (
                     {
@@ -66,7 +70,7 @@ class ClaimController(base.ClaimBase):
                     self.__get(id)
                 )
 
-            except (utils.NoResult, exceptions.MalformedID()):
+            except utils.NoResult:
                 raise exceptions.ClaimDoesNotExist(claim_id, queue, project)
 
     def create(self, queue, metadata, project, limit=10):
@@ -125,9 +129,8 @@ class ClaimController(base.ClaimBase):
         if project is None:
             project = ''
 
-        try:
-            id = utils.cid_decode(claim_id)
-        except exceptions.MalformedID:
+        id = utils.cid_decode(claim_id)
+        if id is None:
             raise exceptions.ClaimDoesNotExist(claim_id, queue, project)
 
         with self.driver('deferred'):
@@ -165,9 +168,8 @@ class ClaimController(base.ClaimBase):
         if project is None:
             project = ''
 
-        try:
-            cid = utils.cid_decode(claim_id)
-        except exceptions.MalformedID:
+        cid = utils.cid_decode(claim_id)
+        if cid is None:
             return
 
         self.driver.run('''
diff --git a/marconi/storage/sqlite/driver.py b/marconi/storage/sqlite/driver.py
index c5736f79e..911284168 100644
--- a/marconi/storage/sqlite/driver.py
+++ b/marconi/storage/sqlite/driver.py
@@ -76,7 +76,7 @@ class Driver(storage.DriverBase):
             return next(self.run(sql, *args))
 
         except StopIteration:
-            raise utils.NoResult
+            raise utils.NoResult()
 
     @property
     def affected(self):
diff --git a/marconi/storage/sqlite/messages.py b/marconi/storage/sqlite/messages.py
index 782d293fa..3fea195f8 100644
--- a/marconi/storage/sqlite/messages.py
+++ b/marconi/storage/sqlite/messages.py
@@ -41,6 +41,10 @@ class MessageController(base.MessageBase):
         if project is None:
             project = ''
 
+        mid = utils.msgid_decode(message_id)
+        if mid is None:
+            raise exceptions.MessageDoesNotExist(message_id, queue, project)
+
         try:
             content, ttl, age = self.driver.get('''
                 select content, ttl, julianday() * 86400.0 - created
@@ -48,24 +52,26 @@ class MessageController(base.MessageBase):
                     on qid = Q.id
                  where ttl > julianday() * 86400.0 - created
                    and M.id = ? and project = ? and name = ?
-            ''', utils.msgid_decode(message_id), project, queue)
-
-            return {
-                'id': message_id,
-                'ttl': ttl,
-                'age': int(age),
-                'body': content,
-            }
+                ''', mid, project, queue)
 
         except utils.NoResult:
             raise exceptions.MessageDoesNotExist(message_id, queue, project)
 
+        return {
+            'id': message_id,
+            'ttl': ttl,
+            'age': int(age),
+            'body': content,
+        }
+
     def bulk_get(self, queue, message_ids, project):
         if project is None:
             project = ''
 
-        message_ids = ["'%s'" % utils.msgid_decode(id) for id in message_ids]
-        message_ids = ','.join(message_ids)
+        message_ids = ','.join(
+            ["'%s'" % id for id in
+             map(utils.msgid_decode, message_ids) if id is not None]
+        )
 
         sql = '''
             select M.id, content, ttl, julianday() * 86400.0 - created
@@ -214,6 +220,8 @@ class MessageController(base.MessageBase):
             project = ''
 
         id = utils.msgid_decode(message_id)
+        if id is None:
+            return
 
         if not claim:
             self.driver.run('''
@@ -240,6 +248,10 @@ class MessageController(base.MessageBase):
 
     def __delete_claimed(self, id, claim):
         # Precondition: id exists in a specific queue
+        cid = utils.cid_decode(claim)
+        if cid is None:
+            return
+
         self.driver.run('''
             delete from Messages
              where id = ?
@@ -248,17 +260,19 @@ class MessageController(base.MessageBase):
                               on id = cid
                            where ttl > julianday() * 86400.0 - created
                              and id = ?)
-        ''', id, utils.cid_decode(claim))
+        ''', id, cid)
 
         if not self.driver.affected:
-            raise exceptions.ClaimNotPermitted(utils.msgid_encode(id), claim)
+            raise exceptions.ClaimNotPermitted(id, claim)
 
     def bulk_delete(self, queue, message_ids, project):
         if project is None:
             project = ''
 
-        message_ids = ','.join(["'%s'" % utils.msgid_decode(id)
-                                for id in message_ids])
+        message_ids = ','.join(
+            ["'%s'" % id for id in
+             map(utils.msgid_decode, message_ids) if id]
+        )
 
         self.driver.run('''
             delete from Messages
diff --git a/marconi/storage/sqlite/utils.py b/marconi/storage/sqlite/utils.py
index 9957f8328..d97f130bf 100644
--- a/marconi/storage/sqlite/utils.py
+++ b/marconi/storage/sqlite/utils.py
@@ -46,7 +46,7 @@ def msgid_encode(id):
         return hex(id ^ 0x5c693a53)[2:]
 
     except TypeError:
-        raise exceptions.MalformedID()
+        return None
 
 
 def msgid_decode(id):
@@ -54,7 +54,7 @@ def msgid_decode(id):
         return int(id, 16) ^ 0x5c693a53
 
     except ValueError:
-        raise exceptions.MalformedID()
+        return None
 
 
 def marker_encode(id):
@@ -78,7 +78,7 @@ def cid_decode(id):
         return int(id, 16) ^ 0x63c9a59c
 
     except ValueError:
-        raise exceptions.MalformedID()
+        return None
 
 
 def julian_to_unix(julian_sec):
diff --git a/marconi/tests/storage/base.py b/marconi/tests/storage/base.py
index 34bb8593a..65184258c 100644
--- a/marconi/tests/storage/base.py
+++ b/marconi/tests/storage/base.py
@@ -363,15 +363,18 @@ class MessageControllerTest(ControllerBaseTest):
         # more likely just list the messages, not try to
         # guess an ID of an arbitrary message.
 
+        # NOTE(cpp-cabrera): A malformed ID should result in an empty
+        # query. Raising an exception for validating IDs makes the
+        # implementation more verbose instead of taking advantage of
+        # the Maybe/Optional protocol, particularly when dealing with
+        # bulk operations.
         queue = 'foo'
         project = '480924'
         self.queue_controller.create(queue, project)
 
         bad_message_id = 'xyz'
-        with testing.expect(exceptions.MalformedID):
-            self.controller.delete(queue, bad_message_id, project)
-
-        with testing.expect(exceptions.MalformedID):
+        self.controller.delete(queue, bad_message_id, project)
+        with testing.expect(exceptions.MessageDoesNotExist):
             self.controller.get(queue, bad_message_id, project)
 
     def test_bad_claim_id(self):
@@ -382,10 +385,9 @@ class MessageControllerTest(ControllerBaseTest):
                                        client_uuid='unused')
 
         bad_claim_id = '; DROP TABLE queues'
-        with testing.expect(exceptions.MalformedID):
-            self.controller.delete('unused', msgid,
-                                   project='480924',
-                                   claim=bad_claim_id)
+        self.controller.delete('unused', msgid,
+                               project='480924',
+                               claim=bad_claim_id)
 
     def test_bad_marker(self):
         queue = 'foo'
diff --git a/marconi/tests/transport/wsgi/test_claims.py b/marconi/tests/transport/wsgi/test_claims.py
index 5f7848c0d..e604a77da 100644
--- a/marconi/tests/transport/wsgi/test_claims.py
+++ b/marconi/tests/transport/wsgi/test_claims.py
@@ -198,6 +198,26 @@ class ClaimsBaseTest(base.TestBase):
                            body='{"ttl": 100, "grace": 60}')
         self.assertEquals(self.srmock.status, falcon.HTTP_404)
 
+    # NOTE(cpp-cabrera): regression test against bug #1203842
+    def test_get_nonexistent_claim_404s(self):
+        path = '/v1/queues/notthere'
+
+        self.simulate_get(path + '/claims/a')
+        self.assertEquals(self.srmock.status, falcon.HTTP_404)
+
+    def test_delete_nonexistent_claim_204s(self):
+        path = '/v1/queues/notthere'
+
+        self.simulate_delete(path + '/claims/a')
+        self.assertEquals(self.srmock.status, falcon.HTTP_204)
+
+    def test_patch_nonexistent_claim_404s(self):
+        path = '/v1/queues/notthere'
+
+        patch_data = json.dumps({'ttl': 100})
+        self.simulate_patch(path + '/claims/a', body=patch_data)
+        self.assertEquals(self.srmock.status, falcon.HTTP_404)
+
 
 class ClaimsMongoDBTests(ClaimsBaseTest):
 
diff --git a/marconi/tests/transport/wsgi/test_messages.py b/marconi/tests/transport/wsgi/test_messages.py
index e7d12683d..25bf9b406 100644
--- a/marconi/tests/transport/wsgi/test_messages.py
+++ b/marconi/tests/transport/wsgi/test_messages.py
@@ -322,6 +322,25 @@ class MessagesBaseTest(base.TestBase):
                           headers=self.headers)
         self.assertEquals(self.srmock.status, falcon.HTTP_200)
 
+    # NOTE(cpp-cabrera): regression test against bug #1203842
+    def test_get_nonexistent_message_404s(self):
+        path = '/v1/queues/notthere'
+
+        self.simulate_get(path + '/messages/a')
+        self.assertEquals(self.srmock.status, falcon.HTTP_404)
+
+    def test_get_multiple_invalid_messages_204s(self):
+        path = '/v1/queues/notthere'
+
+        self.simulate_get(path + '/messages', query_string='ids=a,b,c')
+        self.assertEquals(self.srmock.status, falcon.HTTP_204)
+
+    def test_delete_multiple_invalid_messages_204s(self):
+        path = '/v1/queues/notthere'
+
+        self.simulate_delete(path + '/messages', query_string='ids=a,b,c')
+        self.assertEquals(self.srmock.status, falcon.HTTP_204)
+
     def _post_messages(self, target, repeat=1):
         doc = json.dumps([{'body': 239, 'ttl': 300}] * repeat)
         self.simulate_post(target, self.project_id, body=doc,
diff --git a/marconi/transport/wsgi/messages.py b/marconi/transport/wsgi/messages.py
index 7152c4d22..d03e7415c 100644
--- a/marconi/transport/wsgi/messages.py
+++ b/marconi/transport/wsgi/messages.py
@@ -12,7 +12,6 @@
 # implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
-
 import falcon
 
 from marconi.common import config
@@ -255,8 +254,7 @@ class CollectionResource(object):
             description = _(u'Messages could not be deleted.')
             raise wsgi_exceptions.HTTPServiceUnavailable(description)
 
-        else:
-            resp.status = falcon.HTTP_204
+        resp.status = falcon.HTTP_204
 
 
 class ItemResource(object):