I created https://gaveldown.bid using Apigility, Doctrine in Apigility, slm-queue, Angular 8. Users are authenticated through ebay OAuth2.
Because ebay limits the number of simultaneous requests to 18 I added a Queue with up to 18 workers. Queries are done async with results coming back through a Pusher socket.
This tool allows you to create dozens or hundreds of queries which search on a schedule of 5-20 seconds so you’re the first to see new product listings.