I absolutely love HAProxy ACLs. I use them to rewrite LetsEncrypt requests to another destination so I can cleanly request certificates on the proxy host without downtime or configuring backends or backend servers.

I've also recently migrated one proxy from Traefik to HAProxy, previously I had two proxies, one with T and one with HAP, for different IP ingests, now it's one HAP. Though I don't have failover since the networking in LXC seems to dislike multiple interfaces on the same subnet and doesn't seem to like HAProxy trying to listen on specific interfaces either, that'll have to move to VMs. (I need separated frontends with separate IPs)

The easy part there is that I fully automated HAProxy deployment including certificates with ansible, so moving from container to VM will be a breeze.

Lastly, performance is amazing. I've never had HAProxy even hiccup, even when I got DDoS'd at some point HAProxy held up like a champ.