diff --git a/django_tasks/backends/database/apps.py b/django_tasks/backends/database/apps.py
index d5bec65..d9de15a 100644
--- a/django_tasks/backends/database/apps.py
+++ b/django_tasks/backends/database/apps.py
@@ -5,6 +5,3 @@ class TasksAppConfig(AppConfig):
     name = "django_tasks.backends.database"
     label = "django_tasks_database"
     verbose_name = "Tasks Database Backend"
-
-    def ready(self) -> None:
-        from . import signal_handlers  # noqa
diff --git a/django_tasks/backends/database/migrations/0017_alter_dbtaskresult_run_after.py b/django_tasks/backends/database/migrations/0017_alter_dbtaskresult_run_after.py
new file mode 100644
index 0000000..aa460c8
--- /dev/null
+++ b/django_tasks/backends/database/migrations/0017_alter_dbtaskresult_run_after.py
@@ -0,0 +1,21 @@
+# Generated by Django 5.1.4 on 2025-05-07 19:10
+
+from django.db import migrations
+
+import django_tasks.backends.database.models
+
+
+class Migration(migrations.Migration):
+    dependencies = [
+        ("django_tasks_database", "0016_alter_dbtaskresult_options_and_more"),
+    ]
+
+    operations = [
+        migrations.AlterField(
+            model_name="dbtaskresult",
+            name="run_after",
+            field=django_tasks.backends.database.models.NullIsMaxDateTimeField(
+                verbose_name="run after"
+            ),
+        ),
+    ]
diff --git a/django_tasks/backends/database/models.py b/django_tasks/backends/database/models.py
index 59de8eb..0fe6a93 100644
--- a/django_tasks/backends/database/models.py
+++ b/django_tasks/backends/database/models.py
@@ -50,6 +50,24 @@ def __class_getitem__(cls, _):
 DATE_MAX = datetime.datetime(9999, 1, 1, tzinfo=datetime.timezone.utc)
 
 
+class NullIsMaxDateTimeField(models.DateTimeField):
+    """
+    MySQL can only use indexes on simple queries, so instead of using null,
+    and nulls_last, or models.Case, set null/None as MAX_DATE, and vice-versa
+    """
+
+    def get_prep_value(self, value):  # type: ignore
+        value = super().get_prep_value(value)
+        if value is None:
+            value = DATE_MAX
+        return value
+
+    def from_db_value(self, value, expression, connection):  # type: ignore
+        if value == DATE_MAX:
+            return None
+        return value
+
+
 class DBTaskResultQuerySet(models.QuerySet):
     def ready(self) -> "DBTaskResultQuerySet":
         """
@@ -104,7 +122,7 @@ class DBTaskResult(GenericBase[P, T], models.Model):
     )
     backend_name = models.CharField(_("backend name"), max_length=32)
 
-    run_after = models.DateTimeField(_("run after"))
+    run_after = NullIsMaxDateTimeField(_("run after"))
 
     return_value = models.JSONField(_("return value"), default=None, null=True)
 
@@ -155,7 +173,7 @@ def task(self) -> Task[P, T]:
         return task.using(
             priority=self.priority,
             queue_name=self.queue_name,
-            run_after=None if self.run_after == DATE_MAX else self.run_after,
+            run_after=self.run_after,
             backend=self.backend_name,
         )
 
diff --git a/django_tasks/backends/database/signal_handlers.py b/django_tasks/backends/database/signal_handlers.py
deleted file mode 100644
index 09c0d3b..0000000
--- a/django_tasks/backends/database/signal_handlers.py
+++ /dev/null
@@ -1,12 +0,0 @@
-from typing import Any
-
-from django.db.models.signals import pre_save
-from django.dispatch import receiver
-
-from .models import DATE_MAX, DBTaskResult
-
-
-@receiver(pre_save, sender=DBTaskResult)
-def set_run_after(sender: Any, instance: DBTaskResult, **kwargs: Any) -> None:
-    if instance.run_after is None:
-        instance.run_after = DATE_MAX