Master-Class: Understanding Database Replication (Single, Multi, and Leaderless)

Database Replication is the process of keeping a copy of the same data on multiple nodes. Whether you are aiming for high availability, reduced latency, or horizontal scalability, choosing the right replication algorithm is critical. In this guide, we will explore the three primary algorithms used in modern distributed systems: Single Leader, Multi-Leader, and Leaderless. Table of Contents Single Leader Replication Multi-Leader Replication Leaderless Replication The Replication Lag Problem Summary Comparison 1. Single Leader Replication This is the most common approach (used by MySQL, PostgreSQL, and MongoDB). One node is designated as the leader (master), and all other nodes are followers (read replicas). How it Works Writes: All write requests must be sent to the leader. The leader writes the data locally and sends the change to all followers. Reads: Clients can read from the leader or any follower. Synchronous vs. Asynchronous Synchronous: The leader waits for followers to confirm t