We are working on a cache system for q2a. I think it is a good time to propose a general q2a cache in mysql, as part of core, that all plugins can use.
id: Sequentially incrementing id
owner: module or plugin that owns the cache entry
type: set by owner
idx: The index to the record
idx_crc32: crc32 hash of the idx, this is done for performance, so we only use the crc in our large index. e.g. for url caching, the url is very long, so we don't index it, instead index crc32 of the url.
content: text or blob
index for above:
composite of owner, type, idx_crc32