Performance for SASL server creation is atrocious. Sasl.createSaslServer does not cache the provider resolution for the factories. Factory resolution and server instantiation has 3 major contention points. During bursts of connections, one reader accepting a connection stalls other readers accepting connections, in turn stalling all existing connections handled by those readers.
I benched 5 threads at 187 instances/s - total, not per thread. With this and another change, I've boosted it to 33K instances/s.