How one API error cost an eBay seller £5,000 (and how to prevent it)
A missing inventory sync update led to hundreds of oversold items. Here is how a simple error monitoring system could have saved the day.
We recently took over operations for a large eBay electronics seller. A month prior to joining us, they had a weekend they refer to as "Black Sunday."
Their inventory management system had a silent API failure. It stopped sending stock updates to eBay on Friday night. Over the weekend, a popular discontinued item sold out in their warehouse, but eBay still showed 50 units in stock. By Monday morning, they had oversold 120 orders.
The fallout of silent API failures
The seller had to cancel 120 orders. eBay's algorithm instantly punished them, dropping their seller rating and suppressing their other listings. The lost sales and algorithmic penalty cost them roughly £5,000 in revenue over the next two weeks.
Why it happened
The API failed because of a minor authentication token expiry. That happens. The real problem was that the failure was silent. Nobody was alerted. The system just quietly stopped working.
How to fix it: Defensive Integration
When we build integrations, we build them defensively. Every API sync must have a heartbeat monitor. If the sync fails, or if it doesn't run for 30 minutes, it immediately fires a slack alert to the engineering team. Never trust an API to run perfectly forever; always build an alarm for when it eventually breaks.
Views expressed are those of the author and do not constitute legal or financial advice.