I use it for managing Redis clusters where I have a front-end for a read-write and a front-end for a read-only. I have no idea who else in my company uses it. I had opted to use this because we have silos in our company. We have a network silo that does the load balancing, and I wanted to control how these tests worked with the load balancing. I wanted them to do load balancing where they hand off like a TCP Fast Open. They perform a check on these services with TCP Fast Open.
For example, there is one free HAProxy service for each node, and they use TCP Fast Open for things like that. It's flipped to the HAProxy, and then they establish a persistent connection. It's more of a hand-off, and then I can do all the magic. You can do most of the things I'm doing with HAProxy in F5 too. However, it's siloed off and takes a long time to get things done. I don't have any agility. I took that upon myself with HAProxy because it's a lot quicker to do it myself instead of waiting weeks for somebody else to do it.