Deep-dive developer posts on scaling, system design, OS internals, AI, and the edge cases that break production — every post ships with real, working code.
Start reading →Error: EMFILE: too many open files, open '/var/log/app/access.log'from: Too Many Open Files: Linux File Descriptor Limits in Production
RedBite's API starts throwing EMFILE at 3am, only under load, never in dev. Here's what a file descriptor actually is, why ulimit kills you in production and not locally, and the epoll-based fix that stops leaking them.
Save the order to Postgres, then publish to Kafka. The write between those two lines can fail and you'll never notice — until support tickets show orders that charged but never shipped. The outbox pattern fixes it.
One cache key expires. 2,000 requests land in the same millisecond, all miss, all hit Postgres at once. Here's the thundering herd problem, and the request-coalescing fix that turns 2,000 queries into one.
Transfer money from account A to B at the same moment someone transfers from B to A, and Postgres kills one of them outright. Here's how to reproduce a real deadlock, read the error it gives you, and fix it with lock ordering.
Two requests hit your checkout API at the same millisecond for the last unit in stock. Both succeed. You just oversold. Here's the race condition, and three real fixes: SELECT FOR UPDATE, optimistic locking, and atomic Redis DECR.
A webhook retry isn't an edge case — it's the protocol working as designed. Here's why 'process the webhook' as your handler's whole job doubles orders, and how dedupe keys plus signature verification fix it for real.
