diff --git a/app/celery/celery.py b/app/celery/celery.py
index 23b318692..5fc30a51c 100644
--- a/app/celery/celery.py
+++ b/app/celery/celery.py
@@ -1,31 +1,33 @@
 import time
 
-from flask import current_app
 from celery import Celery, Task
 
 
-class NotifyTask(Task):
-    abstract = True
-    start = None
+def make_task(app):
+    class NotifyTask(Task):
+        abstract = True
+        start = None
 
-    def on_success(self, retval, task_id, args, kwargs):
-        elapsed_time = time.time() - self.start
-        current_app.logger.info(
-            "{task_name} took {time}".format(
-                task_name=self.name, time="{0:.4f}".format(elapsed_time)
+        def on_success(self, retval, task_id, args, kwargs):
+            elapsed_time = time.time() - self.start
+            app.logger.info(
+                "{task_name} took {time}".format(
+                    task_name=self.name, time="{0:.4f}".format(elapsed_time)
+                )
             )
-        )
 
-    def on_failure(self, exc, task_id, args, kwargs, einfo):
-        # ensure task will log exceptions to correct handlers
-        current_app.logger.exception('Celery task failed')
-        super().on_failure(exc, task_id, args, kwargs, einfo)
+        def on_failure(self, exc, task_id, args, kwargs, einfo):
+            # ensure task will log exceptions to correct handlers
+            app.logger.exception('Celery task failed')
+            super().on_failure(exc, task_id, args, kwargs, einfo)
 
-    def __call__(self, *args, **kwargs):
-        # ensure task has flask context to access config, logger, etc
-        with current_app.app_context():
-            self.start = time.time()
-            return super().__call__(*args, **kwargs)
+        def __call__(self, *args, **kwargs):
+            # ensure task has flask context to access config, logger, etc
+            with app.app_context():
+                self.start = time.time()
+                return super().__call__(*args, **kwargs)
+
+    return NotifyTask
 
 
 class NotifyCelery(Celery):
@@ -34,7 +36,7 @@ class NotifyCelery(Celery):
         super().__init__(
             app.import_name,
             broker=app.config['BROKER_URL'],
-            task_cls=NotifyTask,
+            task_cls=make_task(app),
         )
 
         self.conf.update(app.config)
diff --git a/app/celery/service_callback_tasks.py b/app/celery/service_callback_tasks.py
index 52d86f631..4dfe0c953 100644
--- a/app/celery/service_callback_tasks.py
+++ b/app/celery/service_callback_tasks.py
@@ -3,6 +3,7 @@ import json
 from notifications_utils.statsd_decorators import statsd
 
 from app import (
+    db,
     DATETIME_FORMAT,
     notify_celery,
 )
@@ -30,6 +31,9 @@ def send_delivery_status_to_service(self, notification_id):
         # No delivery receipt API info set
         return
 
+    # Release DB connection before performing an external HTTP request
+    db.session.close()
+
     data = {
         "id": str(notification_id),
         "reference": str(notification.client_reference),
diff --git a/manifest-delivery-base.yml b/manifest-delivery-base.yml
index 82bad9b2d..e141c6482 100644
--- a/manifest-delivery-base.yml
+++ b/manifest-delivery-base.yml
@@ -95,6 +95,6 @@ applications:
       NOTIFY_APP_NAME: delivery-worker-receipts
 
   - name: notify-delivery-worker-service-callbacks
-    command: scripts/run_app_paas.sh celery -A run_celery.notify_celery worker --loglevel=INFO --concurrency=11 -Q service-callbacks
+    command: scripts/run_app_paas.sh celery -A run_celery.notify_celery worker --loglevel=INFO -P eventlet -c 1000 -Q service-callbacks
     env:
-      NOTIFY_APP_NAME: delivery-worker-service-callbacks
\ No newline at end of file
+      NOTIFY_APP_NAME: delivery-worker-service-callbacks
diff --git a/run_celery.py b/run_celery.py
index 0b847892e..e21533c86 100644
--- a/run_celery.py
+++ b/run_celery.py
@@ -1,4 +1,5 @@
 #!/usr/bin/env python
+
 from flask import Flask
 
 # notify_celery is referenced from manifest_delivery_base.yml, and cannot be removed