FWIW the spike in " Netstat, established only" in August hasn’t reoccurred, but the Main Overpass API instance has been unreliable for some time now. Suggesting that people “Use alternative servers” is unhelpful as most people’s use of the Overpass API isn’t direct; it’s via third-party tools that either “just fail” or produce unpredictable results when the Overpass API they’re using is unreliable**.
As I mentioned elsewhere I’ve “just used something else” when I’ve wanted to use “something like Overpass” (e.g. Postpass), but alas I suspect that @SimonPoole was right to say “The surprising thing is more that the public Overpass instances have been able to stave off collapse for so long”.
How feasible would “requiring people to be signed into OSM before using Overpass” be?
** and of course it really is the third-party tools that should catch this - some are better than others.