We investigated current rate limits for Mojang API. From documentation we know that all public APIs are rate limited and currently set at 600 requests per 10 minutes. And it's true for the biggest part of endpoints, but not for UUID -> Profile + Skin/Cape endpoint. For this point there such note as "This has a much stricter rate limit: You can request the same profile once per minute, however you can send as many unique requests as you like". And it's confirmed: we easily performed 19k requests from the one IP for about a minute (Mojang, if it affects you, we are really sorry. You know, it's all for science!).