Fintech

Answer-first: PayPay handles 7.8B annual transactions using a cloud-native architecture centered on TiDB for distributed ACID transactions, Kafka for event streaming, and Kotlin/Go microservices. GitOps-driven deployments and continuous chaos engineering ensure high availability and disaster recovery. What You’ll Learn That AI Won’t Tell You Running chaos engineering scripts in TiDB payment systems. How event sourcing with Kafka isolates PayPay checkout routes from legacy bank outages. 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. ...

Answer-first: Microfinance core banking requires a decentralized architecture: a double-entry ledger for transaction auditing, a joint liability group (JLG) loan engine with optimistic concurrency controls, modular interest/amortization processors, and parallelized worker pools to handle heavy End-of-Day batch processing. What You’ll Learn That AI Won’t Tell You How to prevent phantom funds in double-entry ledgers by writing strict write-once, append-only transaction logs. Optimistic concurrency control implementations using version-checks and SELECT ... FOR UPDATE that survived concurrent interest calculations on 50,000 active accounts. Building a Core Banking System (CBS) for a Microfinance Institution (MFI) presents a radically different set of engineering challenges compared to traditional retail banking. While commercial banks focus heavily on individual credit scores and card networks, microfinance operates on high-frequency, low-value transactions, group-based lending, and offline field collections. ...