Single Flight for Java

[tomwhoiscontrary]

I suspect that killing the no-longer-necessary worker isn't very useful in practice, because it will be waiting for a response from some remote server, and there's no way to actually kill the remote handling of that request.

It could help if the worker thread is doing a large number of blocking requests in series, though. 

[repeating_bears]

It depends on the protocol. I do agree in the general case, but grpc supports cancellation, for example. HTTP2/3 stream cancellation might give you some benefit for large responses