Change Data Capture Explained: Syncing Only What Changed in a Database

Change Data Capture (CDC) is a method that sends only the modifications made to a database, such as inserts, updates, and deletes, to another system instead of recopying entire tables. The article uses an online order example, where a status change from 'pending' to 'shipped' can be passed to a reporting system without reloading every order. It contrasts CDC with batch approaches like full refreshes and cursor-based incremental syncs, which rely on timestamps or IDs and may miss some changes. CDC typically reads transaction logs, such as PostgreSQL's Write-Ahead Log or MySQL's binlog, and begins with an initial snapshot before following ongoing changes. The approach is most useful for frequently changing data, though it is not guaranteed to be instantaneous.