Using an intermediate client would go against many of the claimed performance benefits of not using the FK. One would also likely lose the ACI from ACID. Replic

Using an intermediate client would go against many of the claimed performance benefits of not using the FK. One would also likely lose the ACI from ACID. Replicating those features in the intermediate client sure is risky; it would require significant expertise. I'd imagine the implementation would leverage transactions, which would be 'round-trip' to the database server and thus the lock contention would still exist and also be substantially worse (due to the round-trip latency).