Building a CDC Pipeline, Part 1: PostgreSQL WAL Internals
This article introduces the fundamentals of Change Data Capture (CDC) in PostgreSQL by exploring the Write-Ahead Log (WAL), which records all data changes for durability and recovery. The WAL, originally designed for crash recovery and replication, serves as the foundation for real-time CDC by providing a sequential, ordered log of database modifications. Understanding WAL internals is essential for building efficient CDC pipelines and optimizing database performance, recovery, and observability.
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DataBuilding a CDC Pipeline, Part 1: PostgreSQL WAL InternalsHow PostgreSQL records every change before your CDC pipeline ever sees it!George ZefkoApr 27, 20261ShareIntroductionLately I have had the chance to work on projects that capture database changes the moment they happen and I thought a good excuse to dig a bit deeper and write up what I have learned.Every production database is a moving target. Rows are inserted, updated, and deleted continuously, and downstream systems need to reflect those changes as quickly as possible. The traditional answer is a periodic batch job. Query for whatever changed in the last hour, transform it, and load it into the target. This works up to a point, but it trades freshness for simplicity.
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