diff --git a/django/core/cache/backends/db.py b/django/core/cache/backends/db.py
index 0e59c6d65e..8844bc8f61 100644
--- a/django/core/cache/backends/db.py
+++ b/django/core/cache/backends/db.py
@@ -11,6 +11,7 @@ except ImportError:
 from django.conf import settings
 from django.core.cache.backends.base import BaseCache, DEFAULT_TIMEOUT
 from django.db import connections, transaction, router, DatabaseError
+from django.db.backends.utils import typecast_timestamp
 from django.utils import timezone, six
 from django.utils.encoding import force_bytes
 
@@ -65,8 +66,13 @@ class DatabaseCache(BaseDatabaseCache):
         if row is None:
             return default
         now = timezone.now()
-
-        if row[2] < now:
+        expires = row[2]
+        if connections[db].features.needs_datetime_string_cast and not isinstance(expires, datetime):
+            # Note: typecasting is needed by some 3rd party database backends.
+            # All core backends work without typecasting, so be careful about
+            # changes here - test suite will NOT pick regressions here.
+            expires = typecast_timestamp(str(expires))
+        if expires < now:
             db = router.db_for_write(self.cache_model_class)
             cursor = connections[db].cursor()
             cursor.execute("DELETE FROM %s "
@@ -112,12 +118,21 @@ class DatabaseCache(BaseDatabaseCache):
         if six.PY3:
             b64encoded = b64encoded.decode('latin1')
         try:
+            # Note: typecasting for datetimes is needed by some 3rd party
+            # database backends. All core backends work without typecasting,
+            # so be careful about changes here - test suite will NOT pick
+            # regressions.
             with transaction.atomic(using=db):
                 cursor.execute("SELECT cache_key, expires FROM %s "
                                "WHERE cache_key = %%s" % table, [key])
                 result = cursor.fetchone()
+                if result:
+                    current_expires = result[1]
+                    if (connections[db].features.needs_datetime_string_cast and not
+                            isinstance(current_expires, datetime)):
+                        current_expires = typecast_timestamp(str(current_expires))
                 exp = connections[db].ops.value_to_db_datetime(exp)
-                if result and (mode == 'set' or (mode == 'add' and result[1] < now)):
+                if result and (mode == 'set' or (mode == 'add' and current_expires < now)):
                     cursor.execute("UPDATE %s SET value = %%s, expires = %%s "
                                    "WHERE cache_key = %%s" % table,
                                    [b64encoded, exp, key])