The dashboard says 1,340 applies. The inbox says 1,120.

transcript

A recruiter says your dashboard is lying. The interviewer asks: how could your design do that?

The dashboard shows 1,340 applies for one job. Her applicant inbox has 1,120. 220 applies that nobody can find.

The candidate's first clue: the number is too high. Too high means double counting. Not lost data.

Suspect one: client apply events. Retries and double taps inflate them. Two: apply clicks that were abandoned, still counted. Three: replaying the event log without deduplication.

The fix splits the sources. Impressions and views come from analytics. There, approximate is fine. Applies come only from the applications database, through CDC. The same rows that feed her inbox.

Keyed by application ID. Upserts, so a replay changes nothing. Then reconcile daily, and alert on drift. A recruiter's complaint becomes your alert instead.

And what do you tell her today? The inbox is right. Exact numbers come from the source of truth. Never from client events.

Full breakdown in the lecture.