Expand description
In-process LRU cache for read queries.
Keys are namespaced by table: "posts:list:limit=20,offset=0".
Invalidation happens on any write to a given table — we simply
blow away every key whose prefix matches "tablename:".
The LRU is behind a Mutex because lru::LruCache::get needs
&mut self (it updates recency). We keep the cache small and
the critical section tiny — a few µs per lookup in the worst case.