Dev log

The 7-day silent bug that almost broke my Cyprus car search

All my dashboards were green. The job ran every night. And for a week, almost no fresh used-car listings actually made it into the index. Here's the part nobody warns you about.

If you're hunting for a used car in Cyprus, the worst thing a search like ours can do is quietly go stale. You don't know it. The page loads. Listings show up. They just happen to be the same listings you saw last week. And whoever built the thing? They're sitting there looking at a green dashboard, drinking coffee, thinking everything's fine.

That was me, for a stretch. The job that pulls fresh listings ran every night. Cron ticked over. The script exited zero. Email said "OK". Meanwhile, the actual success rate was around two percent — about thirty new items out of fifteen hundred attempts. I just didn't have anything wired up to notice.

The bug wasn't the code. It was the metric.

The script was doing exactly what I'd told it to do. The check I'd built — "did the runner exit cleanly?" — answered yes every time. And of course it did. Cron only cares whether the process came back with a smile. It has no opinion on whether the work was useful.

Once I figured that out, the fix was small. I added a second rule: a quality floor. Compare today's success ratio to a rolling baseline of the last few weeks, and if it drops a long way below that, page someone. Exit codes still get checked, because they catch a different kind of broken (the runner died), but they're not the only signal anymore.

Why it matters if you're shopping for a car here

AllCars exists so you don't have to hop between five tabs to find a fair price on a 2018 Golf. The whole promise is "fresh, every public listing, no missing cars". The moment that breaks, it's just another stale aggregator with a dark theme.

The lesson is in the runbook now: any time I ship a daily job, it gets a quality-relative-to-baseline rule on day one. Not on day eight, after a customer notices. The new alerts have already caught two unrelated regressions since. Worth it.

If you want the live thing — the one I now actually trust — you can browse Cyprus car listings here. Saved searches notify you the moment a new match appears.