Cianplan

Level 2: Data · L2.2 Replication

Leaderless replication and quorums

Use W + R > N and explain sloppy quorums and read repair.

13 min · Pro

What you take away

  • With no leader, the client writes to several replicas and reads from several; W + R > N forces those sets to overlap.

And 3 more inside the class, in Pro.

How the class is laid out

  1. The problem
  2. The simple version
  3. Tuning N, W and R
  4. Why a quorum is not strong consistency
  5. Single leader
  6. Lag anomalies
  7. Multi-leader
  8. Leaderless
  9. Check your understanding