Articles
Notes on backend architecture, performance work, and the WordPress and Laravel systems I build.
13 min readYour cron ran twice: why exactly-once scheduling does not exist
A job runs at midnight for four years, then runs twice with no deploy. The prime suspect is a daylight-saving fall-back, but there are eight others — clock steps, duplicate schedulers, catch-up controllers, lost acks. How to tell them apart from the logs in ten minutes, and why the real fix is a run key with a unique index rather than a better schedule.
Intermediate- Scheduling
- Reliability
- Distributed Systems
- Operations
12 min readThe auth service is down and users are still logging in: how stateless auth works
A backend interview question with a precise answer — the auth service sits on the issuance path, not the verification path. How locally verified signatures, JWKS caching and asymmetric keys keep requests flowing, exactly which operations are already broken, the revocation you traded away, and how to design the degradation deliberately.
Intermediate- Authentication
- Security
- Reliability
- System Design
14 min readThe cache scheduled the outage: stampedes, avalanches and how to survive midnight
A backend interview classic — 10,000 rps in front of a 1,000 rps database, one cache, one shared TTL, and a database that dies at 00:00:00. What the failure is actually called, why it does not recover on its own, and the full ladder of fixes: TTL jitter, single-flight coalescing, stale-while-revalidate, probabilistic early expiry and load shedding.
Intermediate- Caching
- Reliability
- System Design
- Redis
17 min read800 million requests, one corrupted row: debugging what you cannot reproduce
A senior backend interview question, answered as an investigation. Why "1 in 800 million" and "cannot reproduce" are themselves evidence, how to read the shape of the corruption, how to reconstruct the timeline from binlog and WAL, how to turn one bad row into a population you can query — and how to make the whole bug class impossible afterwards.
Advanced- Debugging
- Concurrency
- Databases
- Reliability