For starters:

- Use a better a GC like Azul's C4.

- Leverage monitoring to shard off hot spots.

- If possible, get away from CPU- & memory-inefficient JVM and dynamic languages.

- Steer clear from ScyllaDB and its radioactive license. And, there's little customer demand for it. Astra DB for a commercial distro or YugabyteDB is from the folks behind Cassandra.

- Optimize persistence with multiple choices of backends that abstract away the underlying datastore: the eases the pain of going through "divorce" from any particular technical solution. Writes vs. Reads ratios, geographic replication, object size, data structure (K/V, tuplestore, time series, files, etc.)