Discord engineering goes into details of how they migrated from Cassandra to ScyllaDB, improved the performance of their reads and writes and rearchitected their backend to support the new load. It is an interesting episode lets get into it

0:00 Intro

1:50 Relational vs Distributed

7:00 The Cassandra Troubles

11:00 SnowFlake vs UUID

14:30 B+Tree

19:20 B+Tree and SSDs

25:30 LSM Trees

31:00 Hot partitions

36:00 Cassandra Garbage Collector Pauses

40:00 Changing the Architecture

45:00 The Data Services

55:00 The Migration

1:02:00 Zoned Named Spaces

1:04:00 Summary

Article here How Discord Stores Trillions of Messages

https://discord.com/blog/how-discord-stores-trillions-of-messages