Frontend and backend bugs in web apps — rendering, routing, APIs, sessions.
After moving a PHP 7.4 app to PHP 8.3, our logs grew to 9 GB a day of null-to-string deprecation notices and filled a disk. We found the real call sites, fixed them by intent instead of blind casts, and blocked new ones in CI.
Event countdowns showed NaN days for iPhone users while Chrome was fine. Our API sent dates like 2024-12-3 9:05:00, which only some engines accept. We switched to strict ISO 8601 with an offset and stopped trusting Date parsing.
Our session timeout banner counted from 0 to 1 and then froze. The interval callback captured the first render's state, so it kept computing 0 + 1 forever. Functional state updates, and a ref-based useInterval hook for callbacks that read props, fixed it for good.
A routine rolling deploy restarted one realtime pod holding 50,000 WebSocket connections. Every client reconnected within two seconds, the auth and history lookups melted, and the storm kept itself alive for 25 minutes. Here is how we drain sockets, pace reconnects and make resume cheap.
After a harmless-looking Express refactor, every Stripe webhook failed verification and paid bookings stayed pending. A global JSON parser consumed the body before constructEvent saw it. How we found it, fixed the route and replayed the missed events.
Every few hours our FastAPI service started failing with QueuePool limit of size 5 overflow 10 reached, then recovered on its own. Two code paths opened SQLAlchemy sessions nobody closed, and only the garbage collector gave the connections back. Full repro, fix and pool monitoring inside.
After upgrading to Next.js 15 our dev console filled with sync dynamic API warnings, and one un-awaited auth helper quietly stopped redirecting logged-out users. How we migrated cookies(), headers() and params safely.
After moving our PHP app to a new Ubuntu 24.04 server, every page returned 502 Bad Gateway. Fixing socket ownership got us online, then traffic spikes brought the 502s back from an undersized FPM pool. Here is how we fixed both.
Our onboarding page created two draft workspaces per visit in development. StrictMode was blamed and nearly disabled, but the real bug was a non-idempotent POST inside an effect with no cleanup, and it was also happening in production.