By default, use only one worker of each type

playbooks/roles/edxapp/defaults/main.yml

@@ -417,11 +417,11 @@ EDXAPP_REGISTRATION_EXTRA_FIELDS:
 EDXAPP_CELERY_WORKERS:
   - queue: low
     service_variant: cms
-    concurrency: 3
+    concurrency: 1
     monitor: True
   - queue: default
     service_variant: cms
-    concurrency: 4
+    concurrency: 1
     monitor: True
   - queue: high
     service_variant: cms
@@ -433,15 +433,15 @@ EDXAPP_CELERY_WORKERS:
     monitor: True
   - queue: default
     service_variant: lms
-    concurrency: 3
+    concurrency: 1
     monitor: True
   - queue: high
     service_variant: lms
-    concurrency: 4
+    concurrency: 1
     monitor: True
   - queue: high_mem
     service_variant: lms
-    concurrency: 2
+    concurrency: 1
     monitor: False
     max_tasks_per_child: 1