#systems at scale

2 posts · All tags

• How Discord stores trillions of messages: from MongoDB to Cassandra to ScyllaDB

  Oct 3, 2026 14 min read

  How Discord moved chat history from MongoDB to Cassandra to ScyllaDB: time-bucketed partitions, tombstone traps, hot partitions, and Rust request coalescing.

  • #distributed systems
  • #databases
  • #data modeling
  • #systems at scale

• Idempotency keys: how payment APIs make retries safe

  Oct 3, 2026 2 min read

  Notes on how APIs like Stripe use idempotency keys so clients can retry failed requests without charging a customer twice, plus a minimal implementation.

  • #software engineering
  • #distributed systems
  • #api design
  • #systems at scale