diff --git a/changelog.d/7973.misc b/changelog.d/7973.misc
new file mode 100644
index 000000000000..dfe4c03171d6
--- /dev/null
+++ b/changelog.d/7973.misc
@@ -0,0 +1 @@
+Convert various parts of the codebase to async/await.
diff --git a/synapse/appservice/__init__.py b/synapse/appservice/__init__.py
index 032325647233..1ffdc1ed9591 100644
--- a/synapse/appservice/__init__.py
+++ b/synapse/appservice/__init__.py
@@ -15,11 +15,9 @@
 import logging
 import re
 
-from twisted.internet import defer
-
 from synapse.api.constants import EventTypes
 from synapse.types import GroupID, get_domain_from_id
-from synapse.util.caches.descriptors import cachedInlineCallbacks
+from synapse.util.caches.descriptors import cached
 
 logger = logging.getLogger(__name__)
 
@@ -43,7 +41,7 @@ def send(self, as_api):
         Args:
             as_api(ApplicationServiceApi): The API to use to send.
         Returns:
-            A Deferred which resolves to True if the transaction was sent.
+            An Awaitable which resolves to True if the transaction was sent.
         """
         return as_api.push_bulk(
             service=self.service, events=self.events, txn_id=self.id
@@ -172,8 +170,7 @@ def _is_exclusive(self, ns_key, test_string):
             return regex_obj["exclusive"]
         return False
 
-    @defer.inlineCallbacks
-    def _matches_user(self, event, store):
+    async def _matches_user(self, event, store):
         if not event:
             return False
 
@@ -188,12 +185,12 @@ def _matches_user(self, event, store):
         if not store:
             return False
 
-        does_match = yield self._matches_user_in_member_list(event.room_id, store)
+        does_match = await self._matches_user_in_member_list(event.room_id, store)
         return does_match
 
-    @cachedInlineCallbacks(num_args=1, cache_context=True)
-    def _matches_user_in_member_list(self, room_id, store, cache_context):
-        member_list = yield store.get_users_in_room(
+    @cached(num_args=1, cache_context=True)
+    async def _matches_user_in_member_list(self, room_id, store, cache_context):
+        member_list = await store.get_users_in_room(
             room_id, on_invalidate=cache_context.invalidate
         )
 
@@ -208,35 +205,33 @@ def _matches_room_id(self, event):
             return self.is_interested_in_room(event.room_id)
         return False
 
-    @defer.inlineCallbacks
-    def _matches_aliases(self, event, store):
+    async def _matches_aliases(self, event, store):
         if not store or not event:
             return False
 
-        alias_list = yield store.get_aliases_for_room(event.room_id)
+        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
 
-    @defer.inlineCallbacks
-    def is_interested(self, event, store=None):
+    async def is_interested(self, event, store=None) -> bool:
         """Check if this service is interested in this event.
 
         Args:
             event(Event): The event to check.
             store(DataStore)
         Returns:
-            bool: True if this service would like to know about this event.
+            True if this service would like to know about this event.
         """
         # Do cheap checks first
         if self._matches_room_id(event):
             return True
 
-        if (yield self._matches_aliases(event, store)):
+        if await self._matches_aliases(event, store):
             return True
 
-        if (yield self._matches_user(event, store)):
+        if await self._matches_user(event, store):
             return True
 
         return False
diff --git a/synapse/appservice/api.py b/synapse/appservice/api.py
index 1e0e4d497d60..db578bda79f5 100644
--- a/synapse/appservice/api.py
+++ b/synapse/appservice/api.py
@@ -93,13 +93,12 @@ def __init__(self, hs):
             hs, "as_protocol_meta", timeout_ms=HOUR_IN_MS
         )
 
-    @defer.inlineCallbacks
-    def query_user(self, service, user_id):
+    async def query_user(self, service, user_id):
         if service.url is None:
             return False
         uri = service.url + ("/users/%s" % urllib.parse.quote(user_id))
         try:
-            response = yield self.get_json(uri, {"access_token": service.hs_token})
+            response = await self.get_json(uri, {"access_token": service.hs_token})
             if response is not None:  # just an empty json object
                 return True
         except CodeMessageException as e:
@@ -110,14 +109,12 @@ def query_user(self, service, user_id):
             logger.warning("query_user to %s threw exception %s", uri, ex)
         return False
 
-    @defer.inlineCallbacks
-    def query_alias(self, service, alias):
+    async def query_alias(self, service, alias):
         if service.url is None:
             return False
         uri = service.url + ("/rooms/%s" % urllib.parse.quote(alias))
-        response = None
         try:
-            response = yield self.get_json(uri, {"access_token": service.hs_token})
+            response = await self.get_json(uri, {"access_token": service.hs_token})
             if response is not None:  # just an empty json object
                 return True
         except CodeMessageException as e:
@@ -128,8 +125,7 @@ def query_alias(self, service, alias):
             logger.warning("query_alias to %s threw exception %s", uri, ex)
         return False
 
-    @defer.inlineCallbacks
-    def query_3pe(self, service, kind, protocol, fields):
+    async def query_3pe(self, service, kind, protocol, fields):
         if kind == ThirdPartyEntityKind.USER:
             required_field = "userid"
         elif kind == ThirdPartyEntityKind.LOCATION:
@@ -146,7 +142,7 @@ def query_3pe(self, service, kind, protocol, fields):
             urllib.parse.quote(protocol),
         )
         try:
-            response = yield self.get_json(uri, fields)
+            response = await self.get_json(uri, fields)
             if not isinstance(response, list):
                 logger.warning(
                     "query_3pe to %s returned an invalid response %r", uri, response
@@ -202,8 +198,7 @@ def _get():
         key = (service.id, protocol)
         return self.protocol_meta_cache.wrap(key, _get)
 
-    @defer.inlineCallbacks
-    def push_bulk(self, service, events, txn_id=None):
+    async def push_bulk(self, service, events, txn_id=None):
         if service.url is None:
             return True
 
@@ -218,7 +213,7 @@ def push_bulk(self, service, events, txn_id=None):
 
         uri = service.url + ("/transactions/%s" % urllib.parse.quote(txn_id))
         try:
-            yield self.put_json(
+            await self.put_json(
                 uri=uri,
                 json_body={"events": events},
                 args={"access_token": service.hs_token},
diff --git a/synapse/appservice/scheduler.py b/synapse/appservice/scheduler.py
index 9998f822f1db..d5204b131475 100644
--- a/synapse/appservice/scheduler.py
+++ b/synapse/appservice/scheduler.py
@@ -50,8 +50,6 @@
 """
 import logging
 
-from twisted.internet import defer
-
 from synapse.appservice import ApplicationServiceState
 from synapse.logging.context import run_in_background
 from synapse.metrics.background_process_metrics import run_as_background_process
@@ -73,12 +71,11 @@ def __init__(self, hs):
         self.txn_ctrl = _TransactionController(self.clock, self.store, self.as_api)
         self.queuer = _ServiceQueuer(self.txn_ctrl, self.clock)
 
-    @defer.inlineCallbacks
-    def start(self):
+    async def start(self):
         logger.info("Starting appservice scheduler")
 
         # check for any DOWN ASes and start recoverers for them.
-        services = yield self.store.get_appservices_by_state(
+        services = await self.store.get_appservices_by_state(
             ApplicationServiceState.DOWN
         )
 
@@ -117,8 +114,7 @@ def enqueue(self, service, event):
             "as-sender-%s" % (service.id,), self._send_request, service
         )
 
-    @defer.inlineCallbacks
-    def _send_request(self, service):
+    async def _send_request(self, service):
         # sanity-check: we shouldn't get here if this service already has a sender
         # running.
         assert service.id not in self.requests_in_flight
@@ -130,7 +126,7 @@ def _send_request(self, service):
                 if not events:
                     return
                 try:
-                    yield self.txn_ctrl.send(service, events)
+                    await self.txn_ctrl.send(service, events)
                 except Exception:
                     logger.exception("AS request failed")
         finally:
@@ -162,36 +158,33 @@ def __init__(self, clock, store, as_api):
         # for UTs
         self.RECOVERER_CLASS = _Recoverer
 
-    @defer.inlineCallbacks
-    def send(self, service, events):
+    async def send(self, service, events):
         try:
-            txn = yield self.store.create_appservice_txn(service=service, events=events)
-            service_is_up = yield self._is_service_up(service)
+            txn = await self.store.create_appservice_txn(service=service, events=events)
+            service_is_up = await self._is_service_up(service)
             if service_is_up:
-                sent = yield txn.send(self.as_api)
+                sent = await txn.send(self.as_api)
                 if sent:
-                    yield txn.complete(self.store)
+                    await txn.complete(self.store)
                 else:
                     run_in_background(self._on_txn_fail, service)
         except Exception:
             logger.exception("Error creating appservice transaction")
             run_in_background(self._on_txn_fail, service)
 
-    @defer.inlineCallbacks
-    def on_recovered(self, recoverer):
+    async def on_recovered(self, recoverer):
         logger.info(
             "Successfully recovered application service AS ID %s", recoverer.service.id
         )
         self.recoverers.pop(recoverer.service.id)
         logger.info("Remaining active recoverers: %s", len(self.recoverers))
-        yield self.store.set_appservice_state(
+        await self.store.set_appservice_state(
             recoverer.service, ApplicationServiceState.UP
         )
 
-    @defer.inlineCallbacks
-    def _on_txn_fail(self, service):
+    async def _on_txn_fail(self, service):
         try:
-            yield self.store.set_appservice_state(service, ApplicationServiceState.DOWN)
+            await self.store.set_appservice_state(service, ApplicationServiceState.DOWN)
             self.start_recoverer(service)
         except Exception:
             logger.exception("Error starting AS recoverer")
@@ -211,9 +204,8 @@ def start_recoverer(self, service):
         recoverer.recover()
         logger.info("Now %i active recoverers", len(self.recoverers))
 
-    @defer.inlineCallbacks
-    def _is_service_up(self, service):
-        state = yield self.store.get_appservice_state(service)
+    async def _is_service_up(self, service):
+        state = await self.store.get_appservice_state(service)
         return state == ApplicationServiceState.UP or state is None
 
 
@@ -254,25 +246,24 @@ def _backoff(self):
             self.backoff_counter += 1
         self.recover()
 
-    @defer.inlineCallbacks
-    def retry(self):
+    async def retry(self):
         logger.info("Starting retries on %s", self.service.id)
         try:
             while True:
-                txn = yield self.store.get_oldest_unsent_txn(self.service)
+                txn = await self.store.get_oldest_unsent_txn(self.service)
                 if not txn:
                     # nothing left: we're done!
-                    self.callback(self)
+                    await self.callback(self)
                     return
 
                 logger.info(
                     "Retrying transaction %s for AS ID %s", txn.id, txn.service.id
                 )
-                sent = yield txn.send(self.as_api)
+                sent = await txn.send(self.as_api)
                 if not sent:
                     break
 
-                yield txn.complete(self.store)
+                await txn.complete(self.store)
 
                 # reset the backoff counter and then process the next transaction
                 self.backoff_counter = 1
diff --git a/synapse/handlers/appservice.py b/synapse/handlers/appservice.py
index 92d4c6e16cc4..fbc56c351bce 100644
--- a/synapse/handlers/appservice.py
+++ b/synapse/handlers/appservice.py
@@ -27,7 +27,6 @@
     event_processing_loop_room_count,
 )
 from synapse.metrics.background_process_metrics import run_as_background_process
-from synapse.util import log_failure
 from synapse.util.metrics import Measure
 
 logger = logging.getLogger(__name__)
@@ -100,10 +99,11 @@ async def handle_event(event):
 
                         if not self.started_scheduler:
 
-                            def start_scheduler():
-                                return self.scheduler.start().addErrback(
-                                    log_failure, "Application Services Failure"
-                                )
+                            async def start_scheduler():
+                                try:
+                                    return self.scheduler.start()
+                                except Exception:
+                                    logger.error("Application Services Failure")
 
                             run_as_background_process("as_scheduler", start_scheduler)
                             self.started_scheduler = True
diff --git a/tests/appservice/test_appservice.py b/tests/appservice/test_appservice.py
index 4003869ed665..236b608d5848 100644
--- a/tests/appservice/test_appservice.py
+++ b/tests/appservice/test_appservice.py
@@ -50,13 +50,17 @@ def setUp(self):
     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 self.service.is_interested(self.event)))
+        self.assertTrue(
+            (yield defer.ensureDeferred(self.service.is_interested(self.event)))
+        )
 
     @defer.inlineCallbacks
     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 self.service.is_interested(self.event)))
+        self.assertFalse(
+            (yield defer.ensureDeferred(self.service.is_interested(self.event)))
+        )
 
     @defer.inlineCallbacks
     def test_regex_room_member_is_checked(self):
@@ -64,7 +68,9 @@ def test_regex_room_member_is_checked(self):
         self.event.sender = "@someone_else:matrix.org"
         self.event.type = "m.room.member"
         self.event.state_key = "@irc_foobar:matrix.org"
-        self.assertTrue((yield self.service.is_interested(self.event)))
+        self.assertTrue(
+            (yield defer.ensureDeferred(self.service.is_interested(self.event)))
+        )
 
     @defer.inlineCallbacks
     def test_regex_room_id_match(self):
@@ -72,7 +78,9 @@ def test_regex_room_id_match(self):
             _regex("!some_prefix.*some_suffix:matrix.org")
         )
         self.event.room_id = "!some_prefixs0m3th1nGsome_suffix:matrix.org"
-        self.assertTrue((yield self.service.is_interested(self.event)))
+        self.assertTrue(
+            (yield defer.ensureDeferred(self.service.is_interested(self.event)))
+        )
 
     @defer.inlineCallbacks
     def test_regex_room_id_no_match(self):
@@ -80,19 +88,26 @@ def test_regex_room_id_no_match(self):
             _regex("!some_prefix.*some_suffix:matrix.org")
         )
         self.event.room_id = "!XqBunHwQIXUiqCaoxq:matrix.org"
-        self.assertFalse((yield self.service.is_interested(self.event)))
+        self.assertFalse(
+            (yield defer.ensureDeferred(self.service.is_interested(self.event)))
+        )
 
     @defer.inlineCallbacks
     def test_regex_alias_match(self):
         self.service.namespaces[ApplicationService.NS_ALIASES].append(
             _regex("#irc_.*:matrix.org")
         )
-        self.store.get_aliases_for_room.return_value = [
-            "#irc_foobar:matrix.org",
-            "#athing:matrix.org",
-        ]
-        self.store.get_users_in_room.return_value = []
-        self.assertTrue((yield self.service.is_interested(self.event, self.store)))
+        self.store.get_aliases_for_room.return_value = defer.succeed(
+            ["#irc_foobar:matrix.org", "#athing:matrix.org"]
+        )
+        self.store.get_users_in_room.return_value = defer.succeed([])
+        self.assertTrue(
+            (
+                yield defer.ensureDeferred(
+                    self.service.is_interested(self.event, self.store)
+                )
+            )
+        )
 
     def test_non_exclusive_alias(self):
         self.service.namespaces[ApplicationService.NS_ALIASES].append(
@@ -135,12 +150,17 @@ def test_regex_alias_no_match(self):
         self.service.namespaces[ApplicationService.NS_ALIASES].append(
             _regex("#irc_.*:matrix.org")
         )
-        self.store.get_aliases_for_room.return_value = [
-            "#xmpp_foobar:matrix.org",
-            "#athing:matrix.org",
-        ]
-        self.store.get_users_in_room.return_value = []
-        self.assertFalse((yield self.service.is_interested(self.event, self.store)))
+        self.store.get_aliases_for_room.return_value = defer.succeed(
+            ["#xmpp_foobar:matrix.org", "#athing:matrix.org"]
+        )
+        self.store.get_users_in_room.return_value = defer.succeed([])
+        self.assertFalse(
+            (
+                yield defer.ensureDeferred(
+                    self.service.is_interested(self.event, self.store)
+                )
+            )
+        )
 
     @defer.inlineCallbacks
     def test_regex_multiple_matches(self):
@@ -149,9 +169,17 @@ def test_regex_multiple_matches(self):
         )
         self.service.namespaces[ApplicationService.NS_USERS].append(_regex("@irc_.*"))
         self.event.sender = "@irc_foobar:matrix.org"
-        self.store.get_aliases_for_room.return_value = ["#irc_barfoo:matrix.org"]
-        self.store.get_users_in_room.return_value = []
-        self.assertTrue((yield self.service.is_interested(self.event, self.store)))
+        self.store.get_aliases_for_room.return_value = defer.succeed(
+            ["#irc_barfoo:matrix.org"]
+        )
+        self.store.get_users_in_room.return_value = defer.succeed([])
+        self.assertTrue(
+            (
+                yield defer.ensureDeferred(
+                    self.service.is_interested(self.event, self.store)
+                )
+            )
+        )
 
     @defer.inlineCallbacks
     def test_interested_in_self(self):
@@ -161,19 +189,24 @@ def test_interested_in_self(self):
         self.event.type = "m.room.member"
         self.event.content = {"membership": "invite"}
         self.event.state_key = self.service.sender
-        self.assertTrue((yield self.service.is_interested(self.event)))
+        self.assertTrue(
+            (yield defer.ensureDeferred(self.service.is_interested(self.event)))
+        )
 
     @defer.inlineCallbacks
     def test_member_list_match(self):
         self.service.namespaces[ApplicationService.NS_USERS].append(_regex("@irc_.*"))
-        self.store.get_users_in_room.return_value = [
-            "@alice:here",
-            "@irc_fo:here",  # AS user
-            "@bob:here",
-        ]
-        self.store.get_aliases_for_room.return_value = []
+        # Note that @irc_fo:here is the AS user.
+        self.store.get_users_in_room.return_value = defer.succeed(
+            ["@alice:here", "@irc_fo:here", "@bob:here"]
+        )
+        self.store.get_aliases_for_room.return_value = defer.succeed([])
 
         self.event.sender = "@xmpp_foobar:matrix.org"
         self.assertTrue(
-            (yield self.service.is_interested(event=self.event, store=self.store))
+            (
+                yield defer.ensureDeferred(
+                    self.service.is_interested(event=self.event, store=self.store)
+                )
+            )
         )
diff --git a/tests/appservice/test_scheduler.py b/tests/appservice/test_scheduler.py
index 52f89d3f834e..68a4caabbfdf 100644
--- a/tests/appservice/test_scheduler.py
+++ b/tests/appservice/test_scheduler.py
@@ -25,6 +25,7 @@
 from synapse.logging.context import make_deferred_yieldable
 
 from tests import unittest
+from tests.test_utils import make_awaitable
 
 from ..utils import MockClock
 
@@ -52,11 +53,11 @@ def test_single_service_up_txn_sent(self):
         self.store.get_appservice_state = Mock(
             return_value=defer.succeed(ApplicationServiceState.UP)
         )
-        txn.send = Mock(return_value=defer.succeed(True))
+        txn.send = Mock(return_value=make_awaitable(True))
         self.store.create_appservice_txn = Mock(return_value=defer.succeed(txn))
 
         # actual call
-        self.txnctrl.send(service, events)
+        self.successResultOf(defer.ensureDeferred(self.txnctrl.send(service, events)))
 
         self.store.create_appservice_txn.assert_called_once_with(
             service=service, events=events  # txn made and saved
@@ -77,7 +78,7 @@ def test_single_service_down(self):
         self.store.create_appservice_txn = Mock(return_value=defer.succeed(txn))
 
         # actual call
-        self.txnctrl.send(service, events)
+        self.successResultOf(defer.ensureDeferred(self.txnctrl.send(service, events)))
 
         self.store.create_appservice_txn.assert_called_once_with(
             service=service, events=events  # txn made and saved
@@ -98,11 +99,11 @@ def test_single_service_up_txn_not_sent(self):
             return_value=defer.succeed(ApplicationServiceState.UP)
         )
         self.store.set_appservice_state = Mock(return_value=defer.succeed(True))
-        txn.send = Mock(return_value=defer.succeed(False))  # fails to send
+        txn.send = Mock(return_value=make_awaitable(False))  # fails to send
         self.store.create_appservice_txn = Mock(return_value=defer.succeed(txn))
 
         # actual call
-        self.txnctrl.send(service, events)
+        self.successResultOf(defer.ensureDeferred(self.txnctrl.send(service, events)))
 
         self.store.create_appservice_txn.assert_called_once_with(
             service=service, events=events
@@ -144,7 +145,8 @@ def take_txn(*args, **kwargs):
         self.recoverer.recover()
         # shouldn't have called anything prior to waiting for exp backoff
         self.assertEquals(0, self.store.get_oldest_unsent_txn.call_count)
-        txn.send = Mock(return_value=True)
+        txn.send = Mock(return_value=make_awaitable(True))
+        txn.complete.return_value = make_awaitable(None)
         # wait for exp backoff
         self.clock.advance_time(2)
         self.assertEquals(1, txn.send.call_count)
@@ -169,7 +171,8 @@ def take_txn(*args, **kwargs):
 
         self.recoverer.recover()
         self.assertEquals(0, self.store.get_oldest_unsent_txn.call_count)
-        txn.send = Mock(return_value=False)
+        txn.send = Mock(return_value=make_awaitable(False))
+        txn.complete.return_value = make_awaitable(None)
         self.clock.advance_time(2)
         self.assertEquals(1, txn.send.call_count)
         self.assertEquals(0, txn.complete.call_count)
@@ -182,7 +185,7 @@ def take_txn(*args, **kwargs):
         self.assertEquals(3, txn.send.call_count)
         self.assertEquals(0, txn.complete.call_count)
         self.assertEquals(0, self.callback.call_count)
-        txn.send = Mock(return_value=True)  # successfully send the txn
+        txn.send = Mock(return_value=make_awaitable(True))  # successfully send the txn
         pop_txn = True  # returns the txn the first time, then no more.
         self.clock.advance_time(16)
         self.assertEquals(1, txn.send.call_count)  # new mock reset call count
diff --git a/tests/handlers/test_appservice.py b/tests/handlers/test_appservice.py
index ebabe9a7d64b..628f7d8db031 100644
--- a/tests/handlers/test_appservice.py
+++ b/tests/handlers/test_appservice.py
@@ -19,6 +19,7 @@
 
 from synapse.handlers.appservice import ApplicationServicesHandler
 
+from tests.test_utils import make_awaitable
 from tests.utils import MockClock
 
 from .. import unittest
@@ -117,7 +118,7 @@ def test_query_room_alias_exists(self):
             self._mkservice_alias(is_interested_in_alias=False),
         ]
 
-        self.mock_as_api.query_alias.return_value = defer.succeed(True)
+        self.mock_as_api.query_alias.return_value = make_awaitable(True)
         self.mock_store.get_app_services.return_value = services
         self.mock_store.get_association_from_room_alias.return_value = defer.succeed(
             Mock(room_id=room_id, servers=servers)
@@ -135,7 +136,7 @@ def test_query_room_alias_exists(self):
 
     def _mkservice(self, is_interested):
         service = Mock()
-        service.is_interested.return_value = defer.succeed(is_interested)
+        service.is_interested.return_value = make_awaitable(is_interested)
         service.token = "mock_service_token"
         service.url = "mock_service_url"
         return service