diff --git a/synapse/storage/_base.py b/synapse/storage/_base.py
index a0c1718c2..4ac61be89 100644
--- a/synapse/storage/_base.py
+++ b/synapse/storage/_base.py
@@ -837,11 +837,11 @@ class SQLBaseStore(object):
             return curr_time
 
         logger.debug("Got js: %r", js)
-        d = json.loads(js)
+        d = json.loads(str(js).decode("utf8"))
         start_time = update_counter("decode_json", start_time)
 
         logger.debug("Got internal_metadata: %r", internal_metadata)
-        internal_metadata = json.loads(internal_metadata)
+        internal_metadata = json.loads(str(internal_metadata).decode("utf8"))
         start_time = update_counter("decode_internal", start_time)
 
         ev = FrozenEvent(d, internal_metadata_dict=internal_metadata)
diff --git a/synapse/storage/events.py b/synapse/storage/events.py
index 514feebcb..3b3416716 100644
--- a/synapse/storage/events.py
+++ b/synapse/storage/events.py
@@ -179,7 +179,7 @@ class EventsStore(SQLBaseStore):
                 )
                 txn.execute(
                     sql,
-                    (metadata_json.decode("UTF-8"), event.event_id,)
+                    (buffer(metadata_json), event.event_id,)
                 )
 
                 sql = (
@@ -224,14 +224,14 @@ class EventsStore(SQLBaseStore):
             values={
                 "event_id": event.event_id,
                 "room_id": event.room_id,
-                "internal_metadata": metadata_json.decode("UTF-8"),
-                "json": encode_canonical_json(event_dict).decode("UTF-8"),
+                "internal_metadata": buffer(metadata_json),
+                "json": buffer(encode_canonical_json(event_dict)),
             },
         )
 
-        content = encode_canonical_json(
+        content = buffer(encode_canonical_json(
             event.content
-        ).decode("UTF-8")
+        ))
 
         vals = {
             "topological_ordering": event.depth,
@@ -256,9 +256,9 @@ class EventsStore(SQLBaseStore):
             ]
         }
 
-        vals["unrecognized_keys"] = encode_canonical_json(
+        vals["unrecognized_keys"] = buffer(encode_canonical_json(
             unrec
-        ).decode("UTF-8")
+        ))
 
         sql = (
             "INSERT INTO events"
diff --git a/synapse/storage/schema/full_schemas/11/presence.sql b/synapse/storage/schema/full_schemas/11/presence.sql
index 273e61281..00d803a5c 100644
--- a/synapse/storage/schema/full_schemas/11/presence.sql
+++ b/synapse/storage/schema/full_schemas/11/presence.sql
@@ -17,20 +17,22 @@ CREATE TABLE IF NOT EXISTS presence(
   state VARCHAR(20),
   status_msg VARCHAR(150),
   mtime BIGINT, -- miliseconds since last state change
-  UNIQUE(user_id)
+  UNIQUE (user_id)
 ) ;
 
 -- For each of /my/ users which possibly-remote users are allowed to see their
 -- presence state
 CREATE TABLE IF NOT EXISTS presence_allow_inbound(
   observed_user_id VARCHAR(150) NOT NULL,
-  observer_user_id VARCHAR(150) -- a UserID,
+  observer_user_id VARCHAR(150) NOT NULL, -- a UserID,
+  UNIQUE (observed_user_id, observer_user_id)
 ) ;
 
 -- For each of /my/ users (watcher), which possibly-remote users are they
 -- watching?
 CREATE TABLE IF NOT EXISTS presence_list(
   user_id VARCHAR(150) NOT NULL,
-  observed_user_id VARCHAR(150), -- a UserID,
-  accepted BOOLEAN
+  observed_user_id VARCHAR(150) NOT NULL, -- a UserID,
+  accepted BOOLEAN NOT NULL,
+  UNIQUE (user_id, observed_user_id)
 ) ;
diff --git a/synapse/storage/schema/full_schemas/11/users.sql b/synapse/storage/schema/full_schemas/11/users.sql
index 0271de352..ba0f42d45 100644
--- a/synapse/storage/schema/full_schemas/11/users.sql
+++ b/synapse/storage/schema/full_schemas/11/users.sql
@@ -35,8 +35,8 @@ CREATE TABLE IF NOT EXISTS user_ips (
     device_id VARCHAR(150),
     ip VARCHAR(150) NOT NULL,
     user_agent VARCHAR(150) NOT NULL,
-    last_seen BIGINT NOT NULL,
-    UNIQUE (user, access_token, ip, user_agent)
+    last_seen BIGINT NOT NULL
 ) ;
 
 CREATE INDEX IF NOT EXISTS user_ips_user ON user_ips(user);
+CREATE INDEX IF NOT EXISTS user_ips_user_ip ON user_ips(user, access_token, ip);