HTTP methods and status codes that trip up backend interviews
7 min read A working reference for HTTP methods and status codes, with the safe-versus-idempotent distinction and the codes interviewers keep probing. Read article
System Design
System Design
Designing a payment system that never charges a card twice
6 min read A walkthrough of the payment-system design interview: idempotency keys, a double-entry ledger, PSP failures, and the reconciliation job that catches what code misses. Read article
System Design
Designing a notification system that won’t bury your OTP
6 min read A walkthrough of the notification system design interview: priority queues, fan-out, user preferences, idempotency, and the failure modes interviewers probe. Read article
