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🧩 Change Data Capture (CDC)

CDC (Change Data Capture) is a mechanism providing structure to detect database changes in real-time and deliver them as events to outside.

✅ Overview​

Acquires DB changes (INSERT / UPDATE / DELETE) at log level, and reflects them to stream without going through application.

✅ Problems Addressed​

  • App forgot to fire event even though DB was changed.
  • Flow involving app became complex and consistency cannot be maintained.
  • App cannot withstand high throughput event generation.

By CDC, DB changes are reliably turned into events without going through app.

✅ Basic Philosophy & Structure​

  • Read DB logs (WAL / binlog).
  • Deliver change difference as event.
  • Change to app is unnecessary (DB is sole truth source).

✅ Suitable Cases​

  • Asynchronous replication of massive data.
  • Don't want to write event generation in app.
  • Immediate reflection to data pipeline / analysis platform.

❌ Unsuitable Cases​

  • DB schema changes frequently and is unstable.
  • Want to control all synchronous processing with strong consistency.

✅ Related Styles​

✅ Summary​

CDC is a mechanism balancing consistency and scale by DB-driven event generation.
It is a central technique of modern data architecture in that it can offload event generation, which tends to become complex in applications, to DB.