ephemeral behavior for redis (#2373)

* ephemeral behavior for redis

* notes for redis command line consistency

deployment/docker_compose/docker-compose.search-testing.yml

@@ -209,13 +209,12 @@ services:
     restart: always
     ports:
       - '6379:6379'
-    command: redis-server
-    volumes: 
-      - cache_volume:/data
+    # docker silently mounts /data even without an explicit volume mount, which enables
+    # persistence. explicitly setting save and appendonly forces ephemeral behavior.
+    command: redis-server --save "" --appendonly no
 
 
 volumes:
-  cache_volume:
   db_volume:
     driver: local
     driver_opts: