Possible race conditions with Rails low level caching

With Rails low-level caching, race conditions between cache invalidation and cache writing would lead to cache inconsistency. For example:

• Process A: Fetch from the cache, cache miss. Read user.display_name.
• Process B: Update user.display_name, then invalidate the cache. Process A: Write the previously read user.display_name (which is now stale) to the cache. All subsequent requests would use the stale data from the cache.

With RedisMemo

Since RedisMemo is version-addressable, the race condition would not happen:

• Process A: Fetch from the cache, cache miss. Read user.display_name.
• Process B: Update user.display_name, then bump the dependency version for that user.
• Process A: Write the previously read user.display_name to the cache using the old user dependency version -- it is only referenceable using the old dependency version. All subsequent requests would use the new dependency version process B has just set, data associated with the old dependency version is no longer referenceable, thus the stale data has been discarded.