Hey! Well, aside from rotating multiple user agents, have a cheeky retry and having a "retry" button next to each engine I also heavily cache results so that for 12 hours the same query will give you the same results from cache. You can always invalidate cache from the settings.

Another thing you can also do is add multiple proxy that rotate on each request, traffic goes through proxy urls and you don't get hit with rate limiting (again, proxy settings are in the settings tab - you can find free ones around).

Searches happen asyncronously btw, which means if one engine hangs and fails the others will still return results quickly enough that clicking on the retry button shouldn't be that big of an issue. The biggest engine I have had issues with has been Ecosia, always hitting that pesky cloudflare anti bot page, but that's a third party extension engine, so it doesn't matter too much

So far I haven't been rate limited by google yet, not gonna claim it won't happen as it probably will, it's the nature of the tool, but finger crossed so far so good.