Despite what language it's written in, HAProxy has a very responsive team and it was great to work with them when we had discovered a security issue in it a bit ago.
It took quite a few emails back and forth with them to understand some very subtle interactions in AWS ALB->HAProxy->Backend, and after they issued a fix they even got on a call with us and AWS to discuss the ALB's behavior (although AWS did not change anything sadly).
Amusingly, like 1vuio0pswjnm7's comment, we also temporarily patched it with a HAProxy ACL.
HAProxy is written in C, which has no GC by default. Also, we are talking about "team responsiveness" which sounds more like it is the time that the team needs to react on a bug being reported. So GC pauses can't be what iancaroll meant.
It took quite a few emails back and forth with them to understand some very subtle interactions in AWS ALB->HAProxy->Backend, and after they issued a fix they even got on a call with us and AWS to discuss the ALB's behavior (although AWS did not change anything sadly).
Amusingly, like 1vuio0pswjnm7's comment, we also temporarily patched it with a HAProxy ACL.