diff --git a/changelog.d/11911.misc b/changelog.d/11911.misc
new file mode 100644
index 000000000000..805588c2e963
--- /dev/null
+++ b/changelog.d/11911.misc
@@ -0,0 +1 @@
+Various refactors to the application service notifier code.
\ No newline at end of file
diff --git a/synapse/appservice/__init__.py b/synapse/appservice/__init__.py
index 7dbebd97b5d3..a340a8c9c703 100644
--- a/synapse/appservice/__init__.py
+++ b/synapse/appservice/__init__.py
@@ -165,23 +165,16 @@ def _is_exclusive(self, namespace_key: str, test_string: str) -> bool:
             return namespace.exclusive
         return False
 
-    async def _matches_user(
-        self, event: Optional[EventBase], store: Optional["DataStore"] = None
-    ) -> bool:
-        if not event:
-            return False
-
+    async def _matches_user(self, event: EventBase, store: "DataStore") -> bool:
         if self.is_interested_in_user(event.sender):
             return True
+
         # also check m.room.member state key
         if event.type == EventTypes.Member and self.is_interested_in_user(
             event.state_key
         ):
             return True
 
-        if not store:
-            return False
-
         does_match = await self.matches_user_in_member_list(event.room_id, store)
         return does_match
 
@@ -216,21 +209,15 @@ def _matches_room_id(self, event: EventBase) -> bool:
             return self.is_interested_in_room(event.room_id)
         return False
 
-    async def _matches_aliases(
-        self, event: EventBase, store: Optional["DataStore"] = None
-    ) -> bool:
-        if not store or not event:
-            return False
-
+    async def _matches_aliases(self, event: EventBase, store: "DataStore") -> bool:
         alias_list = await store.get_aliases_for_room(event.room_id)
         for alias in alias_list:
             if self.is_interested_in_alias(alias):
                 return True
+
         return False
 
-    async def is_interested(
-        self, event: EventBase, store: Optional["DataStore"] = None
-    ) -> bool:
+    async def is_interested(self, event: EventBase, store: "DataStore") -> bool:
         """Check if this service is interested in this event.
 
         Args:
diff --git a/synapse/handlers/appservice.py b/synapse/handlers/appservice.py
index 0fb919acf672..a42c3558e42b 100644
--- a/synapse/handlers/appservice.py
+++ b/synapse/handlers/appservice.py
@@ -649,7 +649,7 @@ async def _get_services_for_event(
         """Retrieve a list of application services interested in this event.
 
         Args:
-            event: The event to check. Can be None if alias_list is not.
+            event: The event to check.
         Returns:
             A list of services interested in this event based on the service regex.
         """
diff --git a/tests/appservice/test_appservice.py b/tests/appservice/test_appservice.py
index 07d8105f41d6..9bd6275e92db 100644
--- a/tests/appservice/test_appservice.py
+++ b/tests/appservice/test_appservice.py
@@ -40,13 +40,19 @@ def setUp(self):
         )
 
         self.store = Mock()
+        self.store.get_aliases_for_room = simple_async_mock([])
+        self.store.get_users_in_room = simple_async_mock([])
 
     @defer.inlineCallbacks
     def test_regex_user_id_prefix_match(self):
         self.service.namespaces[ApplicationService.NS_USERS].append(_regex("@irc_.*"))
         self.event.sender = "@irc_foobar:matrix.org"
         self.assertTrue(
-            (yield defer.ensureDeferred(self.service.is_interested(self.event)))
+            (
+                yield defer.ensureDeferred(
+                    self.service.is_interested(self.event, self.store)
+                )
+            )
         )
 
     @defer.inlineCallbacks
@@ -54,7 +60,11 @@ def test_regex_user_id_prefix_no_match(self):
         self.service.namespaces[ApplicationService.NS_USERS].append(_regex("@irc_.*"))
         self.event.sender = "@someone_else:matrix.org"
         self.assertFalse(
-            (yield defer.ensureDeferred(self.service.is_interested(self.event)))
+            (
+                yield defer.ensureDeferred(
+                    self.service.is_interested(self.event, self.store)
+                )
+            )
         )
 
     @defer.inlineCallbacks
@@ -64,7 +74,11 @@ def test_regex_room_member_is_checked(self):
         self.event.type = "m.room.member"
         self.event.state_key = "@irc_foobar:matrix.org"
         self.assertTrue(
-            (yield defer.ensureDeferred(self.service.is_interested(self.event)))
+            (
+                yield defer.ensureDeferred(
+                    self.service.is_interested(self.event, self.store)
+                )
+            )
         )
 
     @defer.inlineCallbacks
@@ -74,7 +88,11 @@ def test_regex_room_id_match(self):
         )
         self.event.room_id = "!some_prefixs0m3th1nGsome_suffix:matrix.org"
         self.assertTrue(
-            (yield defer.ensureDeferred(self.service.is_interested(self.event)))
+            (
+                yield defer.ensureDeferred(
+                    self.service.is_interested(self.event, self.store)
+                )
+            )
         )
 
     @defer.inlineCallbacks
@@ -84,7 +102,11 @@ def test_regex_room_id_no_match(self):
         )
         self.event.room_id = "!XqBunHwQIXUiqCaoxq:matrix.org"
         self.assertFalse(
-            (yield defer.ensureDeferred(self.service.is_interested(self.event)))
+            (
+                yield defer.ensureDeferred(
+                    self.service.is_interested(self.event, self.store)
+                )
+            )
         )
 
     @defer.inlineCallbacks
@@ -183,7 +205,11 @@ def test_interested_in_self(self):
         self.event.content = {"membership": "invite"}
         self.event.state_key = self.service.sender
         self.assertTrue(
-            (yield defer.ensureDeferred(self.service.is_interested(self.event)))
+            (
+                yield defer.ensureDeferred(
+                    self.service.is_interested(self.event, self.store)
+                )
+            )
         )
 
     @defer.inlineCallbacks