Distributed Systems

Keeping copies of the same data on several nodes. Leaders and followers, sync and async, failover, replication lag, multi-leader and leaderless designs, and quorums, each with a step-through animation.

Building single-leader replication with Express, Redis and Nginx, one step at a time: shared state, replication offsets, read-your-writes, resync, and a manual failover that loses an acknowledged write.