How three changes saved Discord from falling apart

In 2022, Discord's engineers were battling multiple issues. The platform was about to fall apart. It had scaled way faster than anticipated. **Disclaimer**: Might contain _slight_ exaggerations for storytelling reasons. Technical facts are depicted as accurately as possible (see sources below). --- Sources: 1.: https://discord.com/blog/how-discord-stores-billions-of-messages 2.: https://discord.com/blog/maxjourney-pushing-discords-limits-with-a-million-plus-online-users-in-a-single-server 3.: https://discord.com/blog/using-rust-to-scale-elixir-for-11-million-concurrent-users 4.: https://discord.com/blog/how-discord-stores-trillions-of-messages --- Chapters: 00:00 Intro 00:26 Discord's architecture 02:24 Cassandra 05:18 Understanding the problem 08:39 Controlling concurrency 13:50 Migrating databases 17:36 The results