diff --git a/synapse/api/auth.py b/synapse/api/auth.py
index 9dbc7993df..0c297cb022 100644
--- a/synapse/api/auth.py
+++ b/synapse/api/auth.py
@@ -144,17 +144,8 @@ class Auth(object):
     @defer.inlineCallbacks
     def check_host_in_room(self, room_id, host):
         with Measure(self.clock, "check_host_in_room"):
-            latest_event_ids = yield self.store.get_latest_event_ids_in_room(room_id)
-
-            logger.debug("calling resolve_state_groups from check_host_in_room")
-            entry = yield self.state.resolve_state_groups(
-                room_id, latest_event_ids
-            )
-
-            ret = yield self.store.is_host_joined(
-                room_id, host, entry.state_group, entry.state
-            )
-            defer.returnValue(ret)
+            latest_event_ids = yield self.store.is_host_joined(room_id, host)
+            defer.returnValue(latest_event_ids)
 
     def _check_joined_room(self, member, user_id, room_id):
         if not member or member.membership != Membership.JOIN:
diff --git a/synapse/handlers/federation.py b/synapse/handlers/federation.py
index a333acc4aa..39d2bee8da 100644
--- a/synapse/handlers/federation.py
+++ b/synapse/handlers/federation.py
@@ -1102,6 +1102,9 @@ class FederationHandler(BaseHandler):
             user_id,
             "leave"
         )
+        # Mark as outlier as we don't have any state for this event; we're not
+        # even in the room.
+        event.internal_metadata.outlier = True
         event = self._sign_event(event)
 
         # Try the host that we succesfully called /make_leave/ on first for
diff --git a/synapse/handlers/user_directory.py b/synapse/handlers/user_directory.py
index d0fb27d5c1..3c8e483b90 100644
--- a/synapse/handlers/user_directory.py
+++ b/synapse/handlers/user_directory.py
@@ -152,7 +152,7 @@ class UserDirectoyHandler(object):
     def _handle_intial_room(self, room_id):
         """Called when we initially fill out user_directory one room at a time
         """
-        is_in_room = yield self.state.get_is_host_in_room(room_id, self.server_name)
+        is_in_room = yield self.store.is_host_joined(room_id, self.server_name)
         if not is_in_room:
             return
 
@@ -210,7 +210,7 @@ class UserDirectoyHandler(object):
                 if not change:
                     # Need to check if the server left the room entirely, if so
                     # we might need to remove all the users in that room
-                    is_in_room = yield self.state.get_is_host_in_room(
+                    is_in_room = yield self.store.is_host_joined(
                         room_id, self.server_name,
                     )
                     if not is_in_room:
@@ -347,7 +347,7 @@ class UserDirectoyHandler(object):
             if not update_user_in_public and not update_user_dir:
                 break
 
-            is_in_room = yield self.state.get_is_host_in_room(
+            is_in_room = yield self.store.is_host_joined(
                 j_room_id, self.server_name,
             )
 
diff --git a/synapse/replication/slave/storage/events.py b/synapse/replication/slave/storage/events.py
index 6cd3a843df..7034f48b50 100644
--- a/synapse/replication/slave/storage/events.py
+++ b/synapse/replication/slave/storage/events.py
@@ -108,7 +108,7 @@ class SlavedEventStore(BaseSlavedStore):
     get_current_state_ids = (
         StateStore.__dict__["get_current_state_ids"]
     )
-    get_state_group_delta = DataStore.get_state_group_delta.__func__
+    get_state_group_delta = StateStore.__dict__["get_state_group_delta"]
     _get_joined_hosts_cache = RoomMemberStore.__dict__["_get_joined_hosts_cache"]
     has_room_changed_since = DataStore.has_room_changed_since.__func__
 
@@ -154,7 +154,6 @@ class SlavedEventStore(BaseSlavedStore):
         DataStore.get_room_events_stream_for_rooms.__func__
     )
     is_host_joined = DataStore.is_host_joined.__func__
-    _is_host_joined = RoomMemberStore.__dict__["_is_host_joined"]
     get_stream_token_for_event = DataStore.get_stream_token_for_event.__func__
 
     _set_before_and_after = staticmethod(DataStore._set_before_and_after)
diff --git a/synapse/replication/tcp/resource.py b/synapse/replication/tcp/resource.py
index 8b2c4c3043..69c46911ec 100644
--- a/synapse/replication/tcp/resource.py
+++ b/synapse/replication/tcp/resource.py
@@ -67,6 +67,7 @@ class ReplicationStreamer(object):
         self.store = hs.get_datastore()
         self.presence_handler = hs.get_presence_handler()
         self.clock = hs.get_clock()
+        self.notifier = hs.get_notifier()
 
         # Current connections.
         self.connections = []
@@ -99,7 +100,7 @@ class ReplicationStreamer(object):
         if not hs.config.send_federation:
             self.federation_sender = hs.get_federation_sender()
 
-        hs.get_notifier().add_replication_callback(self.on_notifier_poke)
+        self.notifier.add_replication_callback(self.on_notifier_poke)
 
         # Keeps track of whether we are currently checking for updates
         self.is_looping = False
diff --git a/synapse/state.py b/synapse/state.py
index 576eb6b788..5b386e3183 100644
--- a/synapse/state.py
+++ b/synapse/state.py
@@ -182,17 +182,6 @@ class StateHandler(object):
         joined_hosts = yield self.store.get_joined_hosts(room_id, entry)
         defer.returnValue(joined_hosts)
 
-    @defer.inlineCallbacks
-    def get_is_host_in_room(self, room_id, host, latest_event_ids=None):
-        if not latest_event_ids:
-            latest_event_ids = yield self.store.get_latest_event_ids_in_room(room_id)
-        logger.debug("calling resolve_state_groups from get_is_host_in_room")
-        entry = yield self.resolve_state_groups(room_id, latest_event_ids)
-        is_host_joined = yield self.store.is_host_joined(
-            room_id, host, entry.state_id, entry.state
-        )
-        defer.returnValue(is_host_joined)
-
     @defer.inlineCallbacks
     def compute_event_context(self, event, old_state=None):
         """Build an EventContext structure for the event.
diff --git a/synapse/storage/roommember.py b/synapse/storage/roommember.py
index 5a9771043d..88e3a6827c 100644
--- a/synapse/storage/roommember.py
+++ b/synapse/storage/roommember.py
@@ -501,40 +501,37 @@ class RoomMemberStore(SQLBaseStore):
 
         defer.returnValue(users_in_room)
 
-    def is_host_joined(self, room_id, host, state_group, state_ids):
-        if not state_group:
-            # If state_group is None it means it has yet to be assigned a
-            # state group, i.e. we need to make sure that calls with a state_group
-            # of None don't hit previous cached calls with a None state_group.
-            # To do this we set the state_group to a new object as object() != object()
-            state_group = object()
+    @defer.inlineCallbacks
+    def is_host_joined(self, room_id, host):
+        if '%' in host or '_' in host:
+            raise Exception("Invalid host name")
 
-        return self._is_host_joined(
-            room_id, host, state_group, state_ids
-        )
+        sql = """
+            SELECT state_key FROM current_state_events AS c
+            INNER JOIN room_memberships USING (event_id)
+            WHERE membership = 'join'
+                AND type = 'm.room.member'
+                AND c.room_id = ?
+                AND state_key LIKE ?
+            LIMIT 1
+        """
 
-    @cachedInlineCallbacks(num_args=3)
-    def _is_host_joined(self, room_id, host, state_group, current_state_ids):
-        # We don't use `state_group`, its there so that we can cache based
-        # on it. However, its important that its never None, since two current_state's
-        # with a state_group of None are likely to be different.
-        # See bulk_get_push_rules_for_room for how we work around this.
-        assert state_group is not None
+        # We do need to be careful to ensure that host doesn't have any wild cards
+        # in it, but we checked above for known ones and we'll check below that
+        # the returned user actually has the correct domain.
+        like_clause = "%:" + host
 
-        for (etype, state_key), event_id in current_state_ids.items():
-            if etype == EventTypes.Member:
-                try:
-                    if get_domain_from_id(state_key) != host:
-                        continue
-                except:
-                    logger.warn("state_key not user_id: %s", state_key)
-                    continue
+        rows = yield self._execute("is_host_joined", None, sql, room_id, like_clause)
 
-                event = yield self.get_event(event_id, allow_none=True)
-                if event and event.content["membership"] == Membership.JOIN:
-                    defer.returnValue(True)
+        if not rows:
+            defer.returnValue(False)
 
-        defer.returnValue(False)
+        user_id = rows[0][0]
+        if get_domain_from_id(user_id) != host:
+            # This can only happen if the host name has something funky in it
+            raise Exception("Invalid host name")
+
+        defer.returnValue(True)
 
     def get_joined_hosts(self, room_id, state_entry):
         state_group = state_entry.state_group
diff --git a/synapse/storage/state.py b/synapse/storage/state.py
index ab5a6bb1df..a33ed61d66 100644
--- a/synapse/storage/state.py
+++ b/synapse/storage/state.py
@@ -20,6 +20,7 @@ from synapse.util.stringutils import to_ascii
 from synapse.storage.engines import PostgresEngine
 
 from twisted.internet import defer
+from collections import namedtuple
 
 import logging
 
@@ -29,6 +30,16 @@ logger = logging.getLogger(__name__)
 MAX_STATE_DELTA_HOPS = 100
 
 
+class _GetStateGroupDelta(namedtuple("_GetStateGroupDelta", ("prev_group", "delta_ids"))):
+    """Return type of get_state_group_delta that implements __len__, which lets
+    us use the itrable flag when caching
+    """
+    __slots__ = []
+
+    def __len__(self):
+        return len(self.delta_ids) if self.delta_ids else 0
+
+
 class StateStore(SQLBaseStore):
     """ Keeps track of the state at a given event.
 
@@ -98,6 +109,7 @@ class StateStore(SQLBaseStore):
             _get_current_state_ids_txn,
         )
 
+    @cached(max_entries=10000, iterable=True)
     def get_state_group_delta(self, state_group):
         """Given a state group try to return a previous group and a delta between
         the old and the new.
@@ -117,7 +129,7 @@ class StateStore(SQLBaseStore):
             )
 
             if not prev_group:
-                return None, None
+                return _GetStateGroupDelta(None, None)
 
             delta_ids = self._simple_select_list_txn(
                 txn,
@@ -128,10 +140,10 @@ class StateStore(SQLBaseStore):
                 retcols=("type", "state_key", "event_id",)
             )
 
-            return prev_group, {
+            return _GetStateGroupDelta(prev_group, {
                 (row["type"], row["state_key"]): row["event_id"]
                 for row in delta_ids
-            }
+            })
         return self.runInteraction(
             "get_state_group_delta",
             _get_state_group_delta_txn,
diff --git a/synapse/util/caches/stream_change_cache.py b/synapse/util/caches/stream_change_cache.py
index c498aee46c..609625b322 100644
--- a/synapse/util/caches/stream_change_cache.py
+++ b/synapse/util/caches/stream_change_cache.py
@@ -96,10 +96,10 @@ class StreamChangeCache(object):
 
         if stream_pos >= self._earliest_known_stream_pos:
             self.metrics.inc_hits()
-            if stream_pos >= max(self._cache):
-                return False
-            else:
-                return True
+            keys = self._cache.keys()
+            i = keys.bisect_right(stream_pos)
+
+            return i < len(keys)
         else:
             self.metrics.inc_misses()
             return True