Hi,

Suppose there's a transactional cache in front of a database that holds current state of some of the records to speed up data reads. What would be a good way to fix the following race condition:

Thread T1 is about to update record R in DB, it isn't initially cached; at the same time T2 tries to read it, gets cache miss, reads R from DB and caches stale value. Step by step:

T1 is about to update R
    T2 tries to read R and gets cache miss
    T2 reads R from DB
T1 changes R in DB
T1 invalidates (or updates) R in cache
T1 commits
    T2 puts old R in cache

Result: cache contains stale data.