You can customize HAProxy (1.6+) routing with embedded Lua. Lua support may need to be enabled during compilation if not already provided by OS package. Here are some resources:

https://www.arpalert.org/src/haproxy-lua-api/1.8/index.html https://www.techietown.info/2016/10/haproxy-with-lua-support... https://github.com/zareenc/haproxy-lua-examples