NOTE
4.6 Replication Architectures
The three common replication topologies: single-leader, multi-leader, and leaderless replication, and the trade-offs each introduces.
This is a historical learning note and may contain outdated or incomplete understanding.
1. Replication Roles
Many replicated systems assign a node to accept writes and propagate them to replicas, but leadership is not the only possible architecture.
2. Main Architectures
2.1 Single-Leader
One leader accepts writes for a replicated dataset; followers copy its changes and may serve reads.
2.2 Multi-Leader
Multiple leaders can accept writes, often in different regions or disconnected environments, and replicate changes to one another.
2.3 Leaderless
Clients or coordinators write to and read from multiple replicas directly, typically using versioning and quorum-like rules.
The right model depends on write locality, conflict tolerance, latency, availability, and failure-recovery requirements.