Sharing Backend Developer Interview Questions

The article recounts a Backend Developer Intern interview at FPT Telecom centered on three practical system-design problems.

The first challenge was race condition prevention, solved with database transactions and pessimistic locking to avoid negative inventory.

The second was payment webhook failure handling for VNPay, with cron jobs used to recheck payment status when IPN callbacks fail.

The third focused on high-traffic scenarios like flash sales, where caching and Redis-based rate limiting help protect system performance.