The same 99 euros every few days, from a dollar figure that drifted
A price alert kept announcing the same Horta to Lisbon fare as a new low. The alerts compared a converted dollar figure, not the price the airline set.
The same Horta to Lisbon alert kept arriving every few days: 99 €, twice in each email, once as a new low and once as cheaper than last time.
The fare cache sells these fares in euros and converts them to dollars at a rate that moves every time a fare is confirmed again. The alerts compared the dollars. Across three emails the stored figure went from 11,200 cents to 11,162, to 11,155, to 11,066, and each dip of a few cents was both a new route low and a price drop. Over the same days the euro figure went the other way, from 98.10 to 98.58. The price was rising, and every email said 99 € because that is what all of them round to.
The airline’s own price was in the response the whole time. Now two new columns keep it, with its currency, and drops are detected on that. Nothing about how fares are keyed or deduplicated changed, and there is no backfill, because the table is append only. Rows from before the change have no source price, so they fall back to dollars with a 2% noise floor. The email now prints one card per trip and keeps the strongest reason.
Three of the new specs fail on the old evaluator. The weekly report’s own idea of a new low still compares dollars, and that is written down as the next thing to fix.