We're building PolyScale.ai[1] that solves the global latency challenges for apps using caching. Clearly that is a different proposition/architecture to database read-replicas, but if the use case is a fit, it's a powerful solution to a hard problem. PolyScale plugs into your existing database and maintains your transactionality and consistency (we automatically invalidate globally). DML queries pass through to the origin db and reads (SELECT’s, SHOW’s) get cached locally at the edge.
We move the database data and query compute closer to the end user for consistent 1ms query execution times at scale. It intelligently manages the cache for every individual SQL query so no configuration is needed, unless of course you want to set manual TTL’s.