What happens to requests in Instance Request Pending Queue when a backend instance gets terminated due to "Exceeded soft private memory limit"?
Based on my external observations of how things work, I suspect there is only a single ingress queue (per service/module) from which requests are only handed to instances which can immediately handle them.
The actual parameters of this single queue (depth, waiting time, etc) would be the indicators driving the automatic/basic instance scaling logic for that service/module - starting and stopping instances.
In such architecture the death of an instance has absolutely no impact on the queued requests, they would simply be dispatched to other instance(s), either already running or specifically started to handle such request.
Note: this is just a theory, though.
I have B* instances running on App Engine(Python env) to serve user facing requests. Sometimes I see B* instances getting terminated due to Exceeded soft private memory limit 
I understand that increasing the instance class will solve the issue but
I have few queries regarding requests that are present in the Instance Pending Queue !
Assume we have 2 instances of B* instance class and we call it let say => I-1, I-2  

What will happen to those requests that are there in I-1 Instance Request Pending Queue after the I-1 instance gets terminated due to some reason? Will those requests gets evicted from the instance queue as this instance got terminated ?
Will the requests in Instance Pending Queue are Dequeued from the Instance Pending Queue for I-1 and will be put in I-2 Request Queue by the Request scheduler as soon as Request Scheduler finds that I-1 is shutting down due to some reason.

Any help regarding understanding these things will be highly appreciated !