diff --git a/hc/api/migrations/0062_auto_20190720_1350.py b/hc/api/migrations/0062_auto_20190720_1350.py
new file mode 100644
index 00000000..c4e428bb
--- /dev/null
+++ b/hc/api/migrations/0062_auto_20190720_1350.py
@@ -0,0 +1,37 @@
+# Generated by Django 2.2.3 on 2019-07-20 13:50
+
+from django.db import migrations, models
+import django.utils.timezone
+
+
+class Migration(migrations.Migration):
+
+    dependencies = [
+        ('api', '0061_webhook_values'),
+    ]
+
+    operations = [
+        migrations.AlterField(
+            model_name='channel',
+            name='kind',
+            field=models.CharField(choices=[('email', 'Email'), ('webhook', 'Webhook'), ('hipchat', 'HipChat'), ('slack', 'Slack'), ('pd', 'PagerDuty'), ('pagertree', 'PagerTree'), ('pagerteam', 'Pager Team'), ('po', 'Pushover'), ('pushbullet', 'Pushbullet'), ('opsgenie', 'OpsGenie'), ('victorops', 'VictorOps'), ('discord', 'Discord'), ('telegram', 'Telegram'), ('sms', 'SMS'), ('zendesk', 'Zendesk'), ('trello', 'Trello'), ('matrix', 'Matrix'), ('whatsapp', 'WhatsApp')], max_length=20),
+        ),
+        migrations.AlterField(
+            model_name='flip',
+            name='processed',
+            field=models.DateTimeField(blank=True, null=True),
+        ),
+        migrations.AlterField(
+            model_name='tokenbucket',
+            name='updated',
+            field=models.DateTimeField(default=django.utils.timezone.now),
+        ),
+        migrations.AddIndex(
+            model_name='check',
+            index=models.Index(condition=models.Q(_negated=True, status='down'), fields=['alert_after'], name='api_check_aa_not_down'),
+        ),
+        migrations.AddIndex(
+            model_name='flip',
+            index=models.Index(condition=models.Q(processed=None), fields=['processed'], name='api_flip_not_processed'),
+        ),
+    ]
diff --git a/hc/api/models.py b/hc/api/models.py
index d7e11e39..32313aa3 100644
--- a/hc/api/models.py
+++ b/hc/api/models.py
@@ -74,6 +74,17 @@ class Check(models.Model):
     alert_after = models.DateTimeField(null=True, blank=True, editable=False)
     status = models.CharField(max_length=6, choices=STATUSES, default="new")
 
+    class Meta:
+        indexes = [
+            # Index for the alert_after field. Excludes rows with status=down.
+            # Used in the sendalerts management command.
+            models.Index(
+                fields=["alert_after"],
+                name="api_check_aa_not_down",
+                condition=~models.Q(status="down"),
+            )
+        ]
+
     def __str__(self):
         return "%s (%d)" % (self.name or self.code, self.id)
 
@@ -640,10 +651,21 @@ class Notification(models.Model):
 class Flip(models.Model):
     owner = models.ForeignKey(Check, models.CASCADE)
     created = models.DateTimeField()
-    processed = models.DateTimeField(null=True, blank=True, db_index=True)
+    processed = models.DateTimeField(null=True, blank=True)
     old_status = models.CharField(max_length=8, choices=STATUSES)
     new_status = models.CharField(max_length=8, choices=STATUSES)
 
+    class Meta:
+        indexes = [
+            # For quickly looking up unprocessed flips.
+            # Used in the sendalerts management command.
+            models.Index(
+                fields=["processed"],
+                name="api_flip_not_processed",
+                condition=models.Q(processed=None),
+            )
+        ]
+
     def send_alerts(self):
         if self.new_status == "up" and self.old_status in ("new", "paused"):
             # Don't send alerts on new->up and paused->up transitions