Do you mean that when you get an update, you both write to the database and perform an update in the cache? If so, you would want it to be a transaction so that the cache and database is not out of sync.

Maybe a write cache, like on hard drives with write back caching. If you first wrote the update to a cache (queue of updates). Then it would be written to both the cache (cached html for instance) and database in one transaction.

But I think it sounds like more trouble than it's worth.