Cloud Bits: Breaking the Double Write – A Guide to Distributed Data Consistency – Distributed Computing Musings

A deep dive into the dual-write problem in distributed systems and how the transactional outbox pattern solves it. Covers two implementation approaches: poll-based outbox (using a background RelayWorker that queries an outbox table and retries failed operations) and CDC-based outbox (using PostgreSQL WAL streaming via pglogrepl or Debezium to push events to Kafka). Includes concrete code examples in Java/Spring Boot and Go, discusses trade-offs between the two approaches, and addresses idempotency requirements for downstream consumers.