Change Data Capture (CDC)

Explain how CDC works and its use cases.

What Is CDC

Change Data Capture tracks data changes (INSERT/UPDATE/DELETE) in a database and streams those changes to downstream systems in near real-time.

How It Works

Most CDC tools (e.g., Debezium) read the database transaction log (MySQL Binlog, PostgreSQL WAL) rather than polling the database, resulting in minimal production load.

Flow

Database transaction log → CDC tool (Debezium) → Kafka topic → Downstream consumers (data warehouse, cache, search index)

Use Cases

• Database sync: Stream OLTP data to an analytics warehouse in near real-time.
• Cache invalidation: Automatically evict Redis cache entries when the database updates.
• Search index sync: Automatically update Elasticsearch when the database changes.
• Audit log: Maintain a complete history of all database changes.

CDC vs Scheduled Batch

CDC achieves near real-time sync (second-level latency); batch sync typically has hour-to-day delays.