Are GAE instances limited to 10 concurrent request?

Question

I've heard from several sources that Google App Engine Instances have a hard limit of 10 concurrent request. I was wondering if someone could clarify what exactly this means.

Does the scheduler block any requests over the 10, or is this enforced through a limit on concurrent threads?

Specifically, does this limit affect Go instances the same way that it does Python and Java?

EDIT: here's the feature request which will allow App Engine Instance to handle more then 10 concurrent request / threads. Allow configurable limit of concurrent requests per instance. Please star it.

Answer 1

As of July 12, 2012, it's the latter. The 10 concurrent limit is enforced through a limit on concurrent threads on every runtime. Most of such cases, our scheduler will try to spin up a new instance.

Please also see the e-mail from jonmac on this thread: https://groups.google.com/d/msg/google-appengine/y-LnZ2WYJ5Q/j_w13F4oSSkJ