Part 2: Event-Driven Architecture — Kafka at Scale, Transactional Outbox & Idempotency
Multi-Language Edition: This chapter is also available in Vietnamese at 📖 Bản tiếng Việt (Vietnamese Edition). Previous Chapter: Part 1 — Microservices & GitOps Blueprint | Series Hub | Next Chapter: Part 3 — Data Infrastructure: From Aurora to TiDB Answer-First: Handling sudden promotional payment spikes of thousands of TPS requires complete decoupling of synchronous ingress requests from asynchronous ledger persistence. PayPay implements an Event-Driven Architecture centered on Apache Kafka. To guarantee zero financial discrepancies between the database and event streams, PayPay utilizes the Transactional Outbox Pattern with Debezium CDC, avoiding dual-write race conditions. Downstream consumer microservices enforce strict idempotency via Redis distributed locks and UUIDv7 idempotency keys, paired with isolated Dead Letter Queues (DLQ) to prevent poisoned payloads from blocking partition processing. ...