Retention · 7 min read
What 40,000 restock alerts taught us about queue fairness
First-come-first-served sounds simple until inventory lands in three warehouses at once.
Queue order sounds like a solved problem — first to join, first notified. It stops being simple the moment stock for one variant lands across three warehouses on three different days.
Partial restocks need partial releases
Releasing the full waitlist against a partial restock guarantees some shoppers arrive to an empty cart. We cap each send to available units and hold the rest of the queue for the next location's stock event.
Fairness is a support cost, not just an ethics question
Every merchant who skipped queue order to notify 'VIP' customers first ended up with more support tickets, not fewer — shoppers compare notes. Strict queue order turned out to be the lower-support-cost choice too.
Forty thousand alerts in, the boring, strictly-fair implementation is still the one we would recommend to a merchant asking for a shortcut.
See queue order in your waitlist
Back in Stock Alerts releases strictly in join order, capped to available units.
See the app