How to Use PostgreSQL Logical Replication in 2025

Why do I use PostgreSQL in this AI age? because PG comes with the best vector search extension — PGVector, and as a Database itself, it is the best relational database ever among the databases I have used before.

This article reflects on recent in-depth experience with PostgreSQL, focusing on logical replication. It explains how PostgreSQL logical replication works, outlines best practices, and highlights key takeaways. The examples and tests are based on PostgreSQL 17 running on Ubuntu 22.04.

1. How PostgreSQL Logical Replication Works

Logical replication in PostgreSQL uses a publish/subscribe model. The source database (publisher) sends changes to one or more target databases (subscribers) based on a defined set of rules. It relies on the Write-Ahead Log (WAL) to capture changes and a replication slot to ensure data consistency. Here’s the detailed breakdown:

1.1 Publication Side(The Source)

• WAL and Logical Decoding

PostgreSQL uses the WAL, a log of all database changes (inserts, updates, deletes), to track modifications. Logical replication decodes this WAL into a human-readable, logical format (e.g., “INSERT INTO table_name VALUES (…)”) instead of the low-level binary format used in physical replication.

This decoding is done via an output plugin, typically pgoutput (the default in PostgreSQL 10+).