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