Engineering Notes
Short notes about real problems from work. Not tutorials, not '10 trends in 2026.' Things I learned by fixing something specific.
Race conditions in page-based subscription billing
2026-04-12How three concurrent requests can drive a balance into the negative — and why the obvious fix is wrong.
postgresconcurrencybillingsaas
LLM routing: when GPT-4 is overkill
2026-03-28A simple per-document model picker that cut my LLM bill by 40% without hurting quality.
llmopenaiclaudecostsaas