Speed up the backend job. This is my favorite game. A programmer should always feel what's good for computers and what's painful to them. Computers reward pain with decreased performance. If you eliminate pain, you get fast and happy computers. Badly structured operations are the root of all evil.
With well chosen algorithms and thoughtful organization of your data, I can make your response delays radically shorten or virtually disappear.
www.szallodak.hu asked me to make their smart search & business logic faster and smarter. They had a complex matching system and accordingly a very slow MySQL query, even with proper indexing. I have rebuilt some tables, made new ones with cron-based auto updates to speed up certain moves, added a few file-based lookups and a very fast (in-memory string based) algorithm to check room availability.
Before optimization: 6000 - 8000 ms (average response time per search)
After optimization: 25 - 45 ms (ca. 200 times faster)