diff --git a/analytics/tests/test_counts.py b/analytics/tests/test_counts.py
index 3184dc7ddc..e31565a8a1 100644
--- a/analytics/tests/test_counts.py
+++ b/analytics/tests/test_counts.py
@@ -51,6 +51,7 @@ from zerver.lib.exceptions import InvitationError
 from zerver.lib.test_classes import ZulipTestCase
 from zerver.lib.timestamp import TimezoneNotUTCException, floor_to_day
 from zerver.lib.topic import DB_TOPIC_NAME
+from zerver.lib.utils import assert_is_not_none
 from zerver.models import (
     Client,
     Huddle,
@@ -1388,11 +1389,13 @@ class TestLoggingCountStats(AnalyticsTestCase):
         assertInviteCountEquals(5)
 
         # Revoking invite should not give you credit
-        do_revoke_user_invite(PreregistrationUser.objects.filter(realm=user.realm).first())
+        do_revoke_user_invite(
+            assert_is_not_none(PreregistrationUser.objects.filter(realm=user.realm).first())
+        )
         assertInviteCountEquals(5)
 
         # Resending invite should cost you
-        do_resend_user_invite_email(PreregistrationUser.objects.first())
+        do_resend_user_invite_email(assert_is_not_none(PreregistrationUser.objects.first()))
         assertInviteCountEquals(6)
 
     def test_messages_read_hour(self) -> None:
@@ -1423,7 +1426,7 @@ class TestLoggingCountStats(AnalyticsTestCase):
 
         self.send_stream_message(user1, stream.name)
         self.send_stream_message(user1, stream.name)
-        do_mark_stream_messages_as_read(user2, stream.recipient_id)
+        do_mark_stream_messages_as_read(user2, assert_is_not_none(stream.recipient_id))
         self.assertEqual(
             3,
             UserCount.objects.filter(property=read_count_property).aggregate(Sum("value"))[
diff --git a/analytics/views/support.py b/analytics/views/support.py
index 0847d41f31..a88c693696 100644
--- a/analytics/views/support.py
+++ b/analytics/views/support.py
@@ -28,6 +28,7 @@ from zerver.lib.actions import (
 from zerver.lib.exceptions import JsonableError
 from zerver.lib.realm_icon import realm_icon_url
 from zerver.lib.subdomains import get_subdomain_from_hostname
+from zerver.lib.utils import assert_is_not_none
 from zerver.models import (
     MultiuseInvite,
     PreregistrationUser,
@@ -119,24 +120,24 @@ def support(request: HttpRequest) -> HttpResponse:
         if len(keys) != 2:
             raise JsonableError(_("Invalid parameters"))
 
-        realm_id = request.POST.get("realm_id")
+        realm_id: str = assert_is_not_none(request.POST.get("realm_id"))
         realm = Realm.objects.get(id=realm_id)
 
         if request.POST.get("plan_type", None) is not None:
-            new_plan_type = int(request.POST.get("plan_type"))
+            new_plan_type = int(assert_is_not_none(request.POST.get("plan_type")))
             current_plan_type = realm.plan_type
             do_change_plan_type(realm, new_plan_type, acting_user=request.user)
             msg = f"Plan type of {realm.string_id} changed from {get_plan_name(current_plan_type)} to {get_plan_name(new_plan_type)} "
             context["success_message"] = msg
         elif request.POST.get("discount", None) is not None:
-            new_discount = Decimal(request.POST.get("discount"))
+            new_discount = Decimal(assert_is_not_none(request.POST.get("discount")))
             current_discount = get_discount_for_realm(realm) or 0
             attach_discount_to_realm(realm, new_discount, acting_user=request.user)
             context[
                 "success_message"
             ] = f"Discount of {realm.string_id} changed to {new_discount}% from {current_discount}%."
         elif request.POST.get("new_subdomain", None) is not None:
-            new_subdomain = request.POST.get("new_subdomain")
+            new_subdomain: str = assert_is_not_none(request.POST.get("new_subdomain"))
             old_subdomain = realm.string_id
             try:
                 check_subdomain_available(new_subdomain)
diff --git a/corporate/lib/stripe.py b/corporate/lib/stripe.py
index 83836166dc..087078d0f5 100644
--- a/corporate/lib/stripe.py
+++ b/corporate/lib/stripe.py
@@ -5,7 +5,7 @@ import secrets
 from datetime import datetime, timedelta
 from decimal import Decimal
 from functools import wraps
-from typing import Callable, Dict, Generator, Optional, Tuple, TypeVar, cast
+from typing import Any, Callable, Dict, Generator, Optional, Tuple, TypeVar, cast
 
 import orjson
 import stripe
@@ -30,6 +30,7 @@ from zerver.lib.exceptions import JsonableError
 from zerver.lib.logging_util import log_to_file
 from zerver.lib.send_email import FromAddress, send_email_to_billing_admins_and_realm_owners
 from zerver.lib.timestamp import datetime_to_timestamp, timestamp_to_datetime
+from zerver.lib.utils import assert_is_not_none
 from zerver.models import Realm, RealmAuditLog, UserProfile, get_system_bot
 from zproject.config import get_secret
 
@@ -516,7 +517,9 @@ def compute_plan_parameters(
     if automanage_licenses:
         next_invoice_date = add_months(billing_cycle_anchor, 1)
     if free_trial:
-        period_end = billing_cycle_anchor + timedelta(days=settings.FREE_TRIAL_DAYS)
+        period_end = billing_cycle_anchor + timedelta(
+            days=assert_is_not_none(settings.FREE_TRIAL_DAYS)
+        )
         next_invoice_date = period_end
     return billing_cycle_anchor, next_invoice_date, period_end, price_per_license
 
@@ -943,10 +946,12 @@ def estimate_annual_recurring_revenue_by_realm() -> Dict[str, int]:  # nocoverag
 
 
 def get_realms_to_default_discount_dict() -> Dict[str, Decimal]:
-    realms_to_default_discount = {}
+    realms_to_default_discount: Dict[str, Any] = {}
     customers = Customer.objects.exclude(default_discount=None).exclude(default_discount=0)
     for customer in customers:
-        realms_to_default_discount[customer.realm.string_id] = customer.default_discount
+        realms_to_default_discount[customer.realm.string_id] = assert_is_not_none(
+            customer.default_discount
+        )
     return realms_to_default_discount
 
 
diff --git a/corporate/tests/test_stripe.py b/corporate/tests/test_stripe.py
index 63f50139ca..0d63c04e53 100644
--- a/corporate/tests/test_stripe.py
+++ b/corporate/tests/test_stripe.py
@@ -90,6 +90,7 @@ from zerver.lib.actions import (
 )
 from zerver.lib.test_classes import ZulipTestCase
 from zerver.lib.timestamp import datetime_to_timestamp, timestamp_to_datetime
+from zerver.lib.utils import assert_is_not_none
 from zerver.models import (
     Message,
     Realm,
@@ -532,7 +533,7 @@ class StripeTest(StripeTestCase):
 
         # Check that we correctly created a Customer object in Stripe
         stripe_customer = stripe_get_customer(
-            Customer.objects.get(realm=user.realm).stripe_customer_id
+            assert_is_not_none(Customer.objects.get(realm=user.realm).stripe_customer_id)
         )
         self.assertEqual(stripe_customer.default_source.id[:5], "card_")
         self.assertTrue(stripe_customer_has_credit_card_as_default_source(stripe_customer))
@@ -642,9 +643,11 @@ class StripeTest(StripeTestCase):
         self.assertEqual(audit_log_entries[3][0], RealmAuditLog.REALM_PLAN_TYPE_CHANGED)
         self.assertEqual(
             orjson.loads(
-                RealmAuditLog.objects.filter(event_type=RealmAuditLog.CUSTOMER_PLAN_CREATED)
-                .values_list("extra_data", flat=True)
-                .first()
+                assert_is_not_none(
+                    RealmAuditLog.objects.filter(event_type=RealmAuditLog.CUSTOMER_PLAN_CREATED)
+                    .values_list("extra_data", flat=True)
+                    .first()
+                )
             )["automanage_licenses"],
             True,
         )
@@ -694,7 +697,7 @@ class StripeTest(StripeTestCase):
             self.upgrade(invoice=True)
         # Check that we correctly created a Customer in Stripe
         stripe_customer = stripe_get_customer(
-            Customer.objects.get(realm=user.realm).stripe_customer_id
+            assert_is_not_none(Customer.objects.get(realm=user.realm).stripe_customer_id)
         )
         self.assertFalse(stripe_customer_has_credit_card_as_default_source(stripe_customer))
         # It can take a second for Stripe to attach the source to the customer, and in
@@ -781,9 +784,11 @@ class StripeTest(StripeTestCase):
         self.assertEqual(audit_log_entries[2][0], RealmAuditLog.REALM_PLAN_TYPE_CHANGED)
         self.assertEqual(
             orjson.loads(
-                RealmAuditLog.objects.filter(event_type=RealmAuditLog.CUSTOMER_PLAN_CREATED)
-                .values_list("extra_data", flat=True)
-                .first()
+                assert_is_not_none(
+                    RealmAuditLog.objects.filter(event_type=RealmAuditLog.CUSTOMER_PLAN_CREATED)
+                    .values_list("extra_data", flat=True)
+                    .first()
+                )
             )["automanage_licenses"],
             False,
         )
@@ -834,7 +839,7 @@ class StripeTest(StripeTestCase):
                 self.upgrade()
 
             stripe_customer = stripe_get_customer(
-                Customer.objects.get(realm=user.realm).stripe_customer_id
+                assert_is_not_none(Customer.objects.get(realm=user.realm).stripe_customer_id)
             )
             self.assertEqual(stripe_customer.default_source.id[:5], "card_")
             self.assertEqual(stripe_customer.description, "zulip (Zulip Dev)")
@@ -894,9 +899,11 @@ class StripeTest(StripeTestCase):
             self.assertEqual(audit_log_entries[3][0], RealmAuditLog.REALM_PLAN_TYPE_CHANGED)
             self.assertEqual(
                 orjson.loads(
-                    RealmAuditLog.objects.filter(event_type=RealmAuditLog.CUSTOMER_PLAN_CREATED)
-                    .values_list("extra_data", flat=True)
-                    .first()
+                    assert_is_not_none(
+                        RealmAuditLog.objects.filter(event_type=RealmAuditLog.CUSTOMER_PLAN_CREATED)
+                        .values_list("extra_data", flat=True)
+                        .first()
+                    )
                 )["automanage_licenses"],
                 True,
             )
@@ -1040,7 +1047,7 @@ class StripeTest(StripeTestCase):
                 self.upgrade(invoice=True)
 
             stripe_customer = stripe_get_customer(
-                Customer.objects.get(realm=user.realm).stripe_customer_id
+                assert_is_not_none(Customer.objects.get(realm=user.realm).stripe_customer_id)
             )
             self.assertEqual(stripe_customer.discount, None)
             self.assertEqual(stripe_customer.email, user.delivery_email)
@@ -1093,9 +1100,11 @@ class StripeTest(StripeTestCase):
             self.assertEqual(audit_log_entries[2][0], RealmAuditLog.REALM_PLAN_TYPE_CHANGED)
             self.assertEqual(
                 orjson.loads(
-                    RealmAuditLog.objects.filter(event_type=RealmAuditLog.CUSTOMER_PLAN_CREATED)
-                    .values_list("extra_data", flat=True)
-                    .first()
+                    assert_is_not_none(
+                        RealmAuditLog.objects.filter(event_type=RealmAuditLog.CUSTOMER_PLAN_CREATED)
+                        .values_list("extra_data", flat=True)
+                        .first()
+                    )
                 )["automanage_licenses"],
                 False,
             )
@@ -1218,7 +1227,7 @@ class StripeTest(StripeTestCase):
             self.upgrade()
         customer = Customer.objects.first()
         assert customer is not None
-        stripe_customer_id = customer.stripe_customer_id
+        stripe_customer_id: str = assert_is_not_none(customer.stripe_customer_id)
         # Check that the Charge used the old quantity, not new_seat_count
         [charge] = stripe.Charge.list(customer=stripe_customer_id)
         self.assertEqual(8000 * self.seat_count, charge.amount)
@@ -2037,9 +2046,10 @@ class StripeTest(StripeTestCase):
         audit_log = RealmAuditLog.objects.get(
             event_type=RealmAuditLog.CUSTOMER_SWITCHED_FROM_MONTHLY_TO_ANNUAL_PLAN
         )
+        extra_data: str = assert_is_not_none(audit_log.extra_data)
         self.assertEqual(audit_log.realm, user.realm)
-        self.assertEqual(orjson.loads(audit_log.extra_data)["monthly_plan_id"], monthly_plan.id)
-        self.assertEqual(orjson.loads(audit_log.extra_data)["annual_plan_id"], annual_plan.id)
+        self.assertEqual(orjson.loads(extra_data)["monthly_plan_id"], monthly_plan.id)
+        self.assertEqual(orjson.loads(extra_data)["annual_plan_id"], annual_plan.id)
 
         invoice_plans_as_needed(self.next_month)
 
@@ -2468,7 +2478,7 @@ class StripeTest(StripeTestCase):
             self.assert_json_success(result)
         invoice_plans_as_needed(self.next_year)
         stripe_customer = stripe_get_customer(
-            Customer.objects.get(realm=user.realm).stripe_customer_id
+            assert_is_not_none(Customer.objects.get(realm=user.realm).stripe_customer_id)
         )
         [invoice, _] = stripe.Invoice.list(customer=stripe_customer.id)
         invoice_params = {
@@ -2518,7 +2528,7 @@ class StripeTest(StripeTestCase):
             self.assert_json_success(result)
         invoice_plans_as_needed(self.next_year + timedelta(days=365))
         stripe_customer = stripe_get_customer(
-            Customer.objects.get(realm=user.realm).stripe_customer_id
+            assert_is_not_none(Customer.objects.get(realm=user.realm).stripe_customer_id)
         )
         [invoice, _, _] = stripe.Invoice.list(customer=stripe_customer.id)
         invoice_params = {
@@ -3460,7 +3470,7 @@ class InvoiceTest(StripeTestCase):
         plan.invoicing_status = CustomerPlan.STARTED
         plan.save(update_fields=["invoicing_status"])
         with self.assertRaises(NotImplementedError):
-            invoice_plan(CustomerPlan.objects.first(), self.now)
+            invoice_plan(assert_is_not_none(CustomerPlan.objects.first()), self.now)
 
     def test_invoice_plan_without_stripe_customer(self) -> None:
         self.local_upgrade(self.seat_count, True, CustomerPlan.ANNUAL)
diff --git a/zerver/lib/soft_deactivation.py b/zerver/lib/soft_deactivation.py
index 733b6c5f23..8a724dd5f4 100644
--- a/zerver/lib/soft_deactivation.py
+++ b/zerver/lib/soft_deactivation.py
@@ -10,6 +10,7 @@ from django.utils.timezone import now as timezone_now
 from sentry_sdk import capture_exception
 
 from zerver.lib.logging_util import log_to_file
+from zerver.lib.utils import assert_is_not_none
 from zerver.models import (
     Message,
     Realm,
@@ -63,12 +64,14 @@ def filter_by_subscription_history(
                 # check belongs in this inner loop, not the outer loop.
                 break
 
+            event_last_message_id = assert_is_not_none(log_entry.event_last_message_id)
+
             if log_entry.event_type == RealmAuditLog.SUBSCRIPTION_DEACTIVATED:
                 # If the event shows the user was unsubscribed after
                 # event_last_message_id, we know they must have been
                 # subscribed immediately before the event.
                 for stream_message in stream_messages:
-                    if stream_message["id"] <= log_entry.event_last_message_id:
+                    if stream_message["id"] <= event_last_message_id:
                         store_user_message_to_insert(stream_message)
                     else:
                         break
@@ -78,12 +81,12 @@ def filter_by_subscription_history(
             ):
                 initial_msg_count = len(stream_messages)
                 for i, stream_message in enumerate(stream_messages):
-                    if stream_message["id"] > log_entry.event_last_message_id:
+                    if stream_message["id"] > event_last_message_id:
                         stream_messages = stream_messages[i:]
                         break
                 final_msg_count = len(stream_messages)
                 if initial_msg_count == final_msg_count:
-                    if stream_messages[-1]["id"] <= log_entry.event_last_message_id:
+                    if stream_messages[-1]["id"] <= event_last_message_id:
                         stream_messages = []
             else:
                 raise AssertionError(f"{log_entry.event_type} is not a subscription event.")
@@ -172,7 +175,7 @@ def add_missing_messages(user_profile: UserProfile) -> None:
 
     all_stream_subscription_logs: DefaultDict[int, List[RealmAuditLog]] = defaultdict(list)
     for log in subscription_logs:
-        all_stream_subscription_logs[log.modified_stream_id].append(log)
+        all_stream_subscription_logs[assert_is_not_none(log.modified_stream_id)].append(log)
 
     recipient_ids = []
     for sub in all_stream_subs:
diff --git a/zerver/lib/upload.py b/zerver/lib/upload.py
index 601f2b08e5..88122486c9 100644
--- a/zerver/lib/upload.py
+++ b/zerver/lib/upload.py
@@ -31,6 +31,7 @@ from PIL.Image import DecompressionBombError
 
 from zerver.lib.avatar_hash import user_avatar_path
 from zerver.lib.exceptions import ErrorCode, JsonableError
+from zerver.lib.utils import assert_is_not_none
 from zerver.models import Attachment, Message, Realm, RealmEmoji, UserProfile
 
 DEFAULT_AVATAR_SIZE = 100
@@ -729,7 +730,7 @@ class S3UploadBackend(ZulipUploadBackend):
 
 
 def write_local_file(type: str, path: str, file_data: bytes) -> None:
-    file_path = os.path.join(settings.LOCAL_UPLOADS_DIR, type, path)
+    file_path = os.path.join(assert_is_not_none(settings.LOCAL_UPLOADS_DIR), type, path)
 
     os.makedirs(os.path.dirname(file_path), exist_ok=True)
     with open(file_path, "wb") as f:
@@ -737,13 +738,13 @@ def write_local_file(type: str, path: str, file_data: bytes) -> None:
 
 
 def read_local_file(type: str, path: str) -> bytes:
-    file_path = os.path.join(settings.LOCAL_UPLOADS_DIR, type, path)
+    file_path = os.path.join(assert_is_not_none(settings.LOCAL_UPLOADS_DIR), type, path)
     with open(file_path, "rb") as f:
         return f.read()
 
 
 def delete_local_file(type: str, path: str) -> bool:
-    file_path = os.path.join(settings.LOCAL_UPLOADS_DIR, type, path)
+    file_path = os.path.join(assert_is_not_none(settings.LOCAL_UPLOADS_DIR), type, path)
     if os.path.isfile(file_path):
         # This removes the file but the empty folders still remain.
         os.remove(file_path)
@@ -754,7 +755,7 @@ def delete_local_file(type: str, path: str) -> bool:
 
 
 def get_local_file_path(path_id: str) -> Optional[str]:
-    local_path = os.path.join(settings.LOCAL_UPLOADS_DIR, "files", path_id)
+    local_path = os.path.join(assert_is_not_none(settings.LOCAL_UPLOADS_DIR), "files", path_id)
     if os.path.isfile(local_path):
         return local_path
     else:
@@ -897,12 +898,16 @@ class LocalUploadBackend(ZulipUploadBackend):
         file_path = user_avatar_path(user_profile)
 
         output_path = os.path.join(
-            settings.LOCAL_UPLOADS_DIR, "avatars", file_path + file_extension
+            assert_is_not_none(settings.LOCAL_UPLOADS_DIR),
+            "avatars",
+            file_path + file_extension,
         )
         if os.path.isfile(output_path):
             return
 
-        image_path = os.path.join(settings.LOCAL_UPLOADS_DIR, "avatars", file_path + ".original")
+        image_path = os.path.join(
+            assert_is_not_none(settings.LOCAL_UPLOADS_DIR), "avatars", file_path + ".original"
+        )
         with open(image_path, "rb") as f:
             image_data = f.read()
         if is_medium:
@@ -942,7 +947,7 @@ class LocalUploadBackend(ZulipUploadBackend):
             secrets.token_urlsafe(18),
             os.path.basename(tarball_path),
         )
-        abs_path = os.path.join(settings.LOCAL_UPLOADS_DIR, "avatars", path)
+        abs_path = os.path.join(assert_is_not_none(settings.LOCAL_UPLOADS_DIR), "avatars", path)
         os.makedirs(os.path.dirname(abs_path), exist_ok=True)
         shutil.copy(tarball_path, abs_path)
         public_url = realm.uri + "/user_avatars/" + path
diff --git a/zerver/lib/user_mutes.py b/zerver/lib/user_mutes.py
index 71389db704..07548e08fc 100644
--- a/zerver/lib/user_mutes.py
+++ b/zerver/lib/user_mutes.py
@@ -3,6 +3,7 @@ from typing import Dict, List, Optional, Set
 
 from zerver.lib.cache import cache_with_key, get_muting_users_cache_key
 from zerver.lib.timestamp import datetime_to_timestamp
+from zerver.lib.utils import assert_is_not_none
 from zerver.models import MutedUser, UserProfile
 
 
@@ -14,7 +15,7 @@ def get_user_mutes(user_profile: UserProfile) -> List[Dict[str, int]]:
     return [
         {
             "id": row["muted_user_id"],
-            "timestamp": datetime_to_timestamp(row["date_muted"]),
+            "timestamp": datetime_to_timestamp(assert_is_not_none(row["date_muted"])),
         }
         for row in rows
     ]
diff --git a/zerver/views/realm_export.py b/zerver/views/realm_export.py
index 2f95dba0c6..50118c31fa 100644
--- a/zerver/views/realm_export.py
+++ b/zerver/views/realm_export.py
@@ -13,6 +13,7 @@ from zerver.lib.exceptions import JsonableError
 from zerver.lib.export import get_realm_exports_serialized
 from zerver.lib.queue import queue_json_publish
 from zerver.lib.response import json_success
+from zerver.lib.utils import assert_is_not_none
 from zerver.models import RealmAuditLog, UserProfile
 
 
@@ -90,7 +91,7 @@ def delete_realm_export(request: HttpRequest, user: UserProfile, export_id: int)
     except RealmAuditLog.DoesNotExist:
         raise JsonableError(_("Invalid data export ID"))
 
-    export_data = orjson.loads(audit_log_entry.extra_data)
+    export_data = orjson.loads(assert_is_not_none(audit_log_entry.extra_data))
     if "deleted_timestamp" in export_data:
         raise JsonableError(_("Export already deleted"))
     do_delete_realm_export(user, audit_log_entry)
diff --git a/zerver/views/streams.py b/zerver/views/streams.py
index a5b11b8f3c..9a1725bc43 100644
--- a/zerver/views/streams.py
+++ b/zerver/views/streams.py
@@ -71,6 +71,7 @@ from zerver.lib.topic import (
     messages_for_topic,
 )
 from zerver.lib.types import Validator
+from zerver.lib.utils import assert_is_not_none
 from zerver.lib.validator import (
     check_bool,
     check_capped_string,
@@ -726,7 +727,9 @@ def get_topics_backend(
     if is_web_public_query:
         realm = get_valid_realm_from_request(request)
         stream = access_web_public_stream(stream_id, realm)
-        result = get_topic_history_for_public_stream(recipient_id=stream.recipient_id)
+        result = get_topic_history_for_public_stream(
+            recipient_id=assert_is_not_none(stream.recipient_id)
+        )
 
     else:
         assert user_profile is not None
@@ -753,7 +756,7 @@ def delete_in_topic(
 ) -> HttpResponse:
     (stream, sub) = access_stream_by_id(user_profile, stream_id)
 
-    messages = messages_for_topic(stream.recipient_id, topic_name)
+    messages = messages_for_topic(assert_is_not_none(stream.recipient_id), topic_name)
     if not stream.is_history_public_to_subscribers():
         # Don't allow the user to delete messages that they don't have access to.
         deletable_message_ids = UserMessage.objects.filter(