Leader-follower (master-slave) replication uses one writable node:
Write path: Client → Leader → Followers (async or sync)
Read path: Client → Leader or Followers
Advantages:
- Simple conflict resolution (leader decides)
- Strong consistency possible with sync replication
- Well-understood failure modes
Disadvantages:
- Leader is write bottleneck
- Failover requires leader election
- Followers may serve stale reads
Most relational databases use this model. Good default choice when write volume fits on one node.