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Why is my GetSellerList API request timing out?
How to optimize GetSellerList to prevent timeouts
There may be other reasons why your GetSellerList request is timing out, but most likely it is due to the amount of data you are asking to be returned. GetSellerList requires a time range be used. If you get a failed GetSellerList for a time range, you then will need to modify that time range until you get a successful call.
30 days (March 1 - 30) = failed
15 days (March 1 - 15) = success, 15 days (March 15 - 30) = success
In general, we would rather you make multiple smaller calls, then 1 huge call to help break up the data and not use so much memory. So essentially, instead of making the call for a large time range, maybe you can make 3 calls for 10 days.....or something of the sort.
With that said, the above also assumes the listings have been spread out over time. If a seller has listed 50k items at one time, then the above would still work, but the time range would have to be incredibly small.
GetSellerList - http://developer.ebay.com/DevZone/XML/docs/Reference/eBay/GetSellerList.html