Chaos Engineering

Multi-Language Edition: This chapter is also available in Vietnamese at 📖 Bản tiếng Việt (Vietnamese Edition). Previous Chapter: Part 3 — Data Infrastructure: From Aurora to TiDB | Series Hub | Next Chapter: Part 5 — Campaign Architecture: Surviving the 10-Billion Yen Surge Answer-First: Delivering five-nines (99.999%) availability for national payment infrastructure requires shifting from reactive disaster recovery to continuous, automated Chaos Engineering in production. PayPay integrates Chaos Mesh into Kubernetes EKS clusters, deliberately injecting pod evictions, network latency, and cross-AZ partitions during normal business hours to validate self-healing invariants. To prevent cascading failures under heavy load, PayPay enforces distributed circuit breaking with Sentinel, client-side exponential backoff with full jitter, and strict gRPC deadline propagation, ensuring localized microservice brownouts never degrade core payment authorization. ...

Multi-Language Edition: This series is also available in Vietnamese at 📖 Bản tiếng Việt (Vietnamese Edition). Answer-First: PayPay is Japan’s dominant mobile payment service, supporting over 70 million registered users, 7.8 billion annual transactions, and peak promotional surges exceeding 1,250 TPS. To deliver 99.999% availability with zero double-spending guarantees, PayPay evolved from monolithic roots to a cloud-native architecture powered by five pillars: Domain-Driven Microservices with ArgoCD GitOps, Event-Driven decoupling via Apache Kafka, Distributed SQL horizontal scale with TiDB Multi-Raft, Proactive resilience via Chaos Mesh, and Sub-10ms real-time ML fraud detection. ...

PayPay Architecture: Scaling to 70M Users & 100k Peak TPS Answer-first: PayPay’s payment architecture scales to 70M users and 100k TPS using microservice domain isolation, distributed transaction Saga patterns, and multi-region database sharding. PayPay launched in October 2018 and grew to 10 million users in just 3 months — a growth rate that no Japanese fintech had ever seen. By 2025, the platform had crossed 70 million registered users and processed 7.8 billion payments per year. Behind this growth is an engineering team that has had to scale not just their infrastructure, but their entire engineering culture: from service standardization and GitOps-driven deployments to chaos engineering and AI-powered fraud detection. ...