Understanding and Reducing PostgreSQL Replication Lag

Replication lag in PostgreSQL occurs when changes made on the primary server take time to reflect on the replica server. Whether you use streaming or logical replication, lag can impact performance, consistency, and system availability. This post covers the types of replication, their differences, lag causes, mathematical formulas for lag estimation, monitoring techniques, and strategies to minimize replication lag. Types of Replication in PostgreSQL Streaming Replication Streaming replication continuously sends Write-Ahead Log (WAL) changes from the primary to one or more replica servers in near real-time. The replica applies the changes sequentially as they're received. This method replicates the entire database and ensures replicas stay synchronized.