What is Change Data Capture (CDC) and how is it implemented?

CDC captures database changes (inserts, updates, deletes) for streaming to other systems. Methods: Log-based (read transaction log - Debezium, most efficient, no query overhead), Trigger-based (database triggers write changes - adds latency), Timestamp-based (poll for recent changes - simple but misses deletes), Diff-based (compare snapshots - resource intensive). Use cases: event sourcing, search index sync, data warehousing, microservices sync. Log-based preferred for production; consider schema evolution.