What is CDC (Change Data Capture)

Definition

Change Data Capture (CDC) is a technique that identifies and captures only the inserts, updates, and deletes made to a source database and streams those changes to downstream systems, keeping targets in sync continuously without repeatedly copying entire tables.

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Moves only changed rows, slashing data volume compared with full reloads
Keeps target systems near-real-time in sync with the source database
Places minimal load on source systems by reading transaction logs rather than scanning tables
Captures deletes and updates that naive incremental loads often miss

Real World Example

A retailer uses log-based CDC to stream order-status changes from its operational database into the analytics lakehouse within seconds, so dashboards reflect cancellations and shipments almost as they happen.

FAQs

How does CDC detect changes?

Log-based CDC reads the database transaction log, while trigger- or timestamp-based methods detect changes through table mechanisms; log-based is usually least intrusive.

Why use CDC instead of full reloads?

CDC transfers only what changed, which is far faster, cheaper, and gentler on source systems than repeatedly copying whole tables.

What is CDC commonly used for?

Real-time replication, keeping analytics platforms fresh, feeding event streams, and synchronising microservices.