How Discord Stores Trillions of Messages

Bo Ingram's account of Discord's migration off vanilla Cassandra to a Rust-based data service layer is one of the more honest scaling stories out there — no rewrite-everything triumphalism, just a clear-eyed walk through where their original design started to show cracks at trillion-row scale and what they changed. The details on data modeling for a chat workload (message ordering, hot partitions, compaction pressure) are transferable to basically any high-write-volume, append-heavy system. One of the better "how it actually broke and what we did about it" posts I've read.

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