If the data that you’re replicating does not change over time, then replication is easy: you just need to copy the data to every node once, and you’re done. All of the difficulty in replication lies in handling changes to replicated data, and that’s what this chapter is about. We will discuss three popular algorithms for replicating changes between nodes: single-leader, multi-leader, and leaderless replication. Almost all distributed databases use one of these three approaches. They all have various pros and cons, which we will examine in detail.
