The number of threads used for concurrent webhook processing is hardcoded to 10, but there are some scenarios where an administrator would like to increase or reduce this number.

For instance, I have several slow processes due to Bitbucket API rate limit. Once 10 of those processes are in progress, no other webhook is being processed (although those other processes would go quite fast because they are from a different user, they are waiting for ages because 10 slow requests are still running)