503 error

Hello all... Every now and then I get a 503 error on my free webapp (I also have a paid one). It's identical to this person's issue (I think he meant 503 instead of 403). I do use Twilio as well. Any ideas? Only every now and then I'll get the 503...

A free web app only has one worker. If that worker is busy for a long time, you may get a 503. We do queue requests for a while, so they can wait for the worker to be free, but we don't queue them forever.

Ok gotcha... thanks!