Parcels Held Back by Short SQS Polling Caused Late Marketplace Despatches

A warehouse despatch job that sends tracking numbers to a major marketplace stopped early after receiving an empty response from Amazon's SQS queue. Because the rewritten Python script used short polling, which queries only a random subset of SQS servers, it treated the empty reply as the queue being empty and left parcels behind for the next day's feed. The late despatch rate rose from under one percent to six in October, triggering a warning from the marketplace, even though the parcels had left the warehouse on time. The fix includes long polling, a longer default wait time on the queue, and requiring two consecutive empty polls before stopping. Added safeguards include a reconciliation check at eleven and an alarm on the age of the oldest message.