Building software

Database Partitioning is when you split the data inside the database into smaller "databases". One partition holds a part of your data. All partitions together form the entire database.

Partitioning is often used with replication, which means each partition's data is copied onto multiple nodes. This way, even though each record is in only one partition, it can be stored on different nodes for fault tolerance. A node may hold more than one partition.

When using a leader-follower replication model, the mix of partitioning and replication might look like this:

Replication lag occurs when there is a delay between a write operation being executed on the primary (leader) node and the same operation being replicated to the secondary (follower) nodes.

Replication lag is a basic issue in leader-based replication systems that are made for better availability, scalability, and faster response times by spreading out read operations across replicas in different locations.