Module 09: Coordination

In a distributed system, individual nodes are unreliable. They crash, they pause, they lose connection. Coordination is the art of getting these unreliable nodes to work together as a single, coherent system.

This module covers the “Hard Parts” of distributed systems:

  1. Leader Election: How do we decide who is in charge?
  2. Distributed Locking: How do we prevent two people from booking the same seat?
  3. Consensus (Raft/Paxos): How do we agree on data when nodes are failing?
  4. ZooKeeper: The industry standard tool for coordination.

The Zero to Hero Journey

  • Junior: Uses a database for everything. Thinks locking is just synchronized.
  • Senior: Uses Redis for locks. Understands the trade-offs of TTLs.
  • Principal: Understands Raft’s log replication. Knows why Redlock isn’t safe for money. Uses ZooKeeper for service discovery.

Let’s begin.

Module Chapters