Read this interesting retro about discords migration path from Mongo to Cassandra to now ScyllaDB.
https://discord.com/blog/how-discord-stores-trillions-of-messages
@prologic@twtxt.net in the article they say they have a p99 of 15ms reading historical data. Which is pretty nuts.. Aside from having close to 900TB of SSD…
I suppose the p90/p50 would be higher. Right? I never remember which way that funnel goes.