Dev log

How AllCars keeps Cyprus car listings reliably fresh

A scheduled job that exits cleanly is not the same as a job that did its work. Here's the small idea — watchdogs — that keeps every used-car listing in Cyprus reliably fresh on AllCars.

If you've used AllCars to browse used cars in Cyprus, the unspoken contract is "the listings I see are real and current". You don't think about it. I can't afford not to.

The catch is that scheduled jobs are not honest reporters of their own work. A job can run on time, finish without crashing, exit zero, send a "completed" line to the log, and still produce nothing useful. I've seen this happen in the wild. More than once.

Trust the artifact, not the runner

The fix is a small idea borrowed from production engineering everywhere: watchdogs. A watchdog doesn't ask "did the job run?". It asks "did the work happen?". Three flavours, three different angles:

Did the artifact change? If a job is supposed to refresh a file or a table, look at when it was last touched. If it's older than the schedule plus a generous buffer, page someone.

Is the success rate normal? Compare today's processed-versus-attempted ratio to a rolling baseline of the last few weeks. A small drop is just a quiet day. A big drop, sustained, means the work isn't happening even if exit codes look fine.

Did the schedule actually fire? The schedule itself is not infallible — sometimes a system swallows a tick. A separate watcher confirms the job at least started in the expected window.

Why this matters when you're searching

Because of these three rules, the freshness of the AllCars index is something I can actually trust. New listings appear within hours, not days. Saved-search alerts arrive when they're supposed to. The deal score reflects the market now, not the market last Tuesday.

The pager is calmer too — I get woken up when something is actually wrong, not when a script forgot to log. Boring, undramatic engineering. Exactly the kind that holds up.