The purpose is not to compare to varnish. If you need a real cache, please use varnish. haproxy is to the cache what varnish is to the load-balancer. Ie: we bot

The purpose is not to compare to varnish. If you need a real cache, please use varnish. haproxy is to the cache what varnish is to the load-balancer. Ie: we both do a little bit of it to simplify certain deployments, but serious ones need both. We did this to address certain regular demands from users of dirty servers suffering from just "GET /favicon.ico" (hence the "favicon cache" term we've been using for a long time). I've been annoyed by seeing people abusing the "errorfile 503" to deliver a few static objects and this is an elegant response to address this. Over time it may turn out that it could combine well with varnish, for example to improve a little bit the scalability of haproxy+varnish nodes, we'll see. But it definitely is not at all an alternative to varnish. As a rule of thumb, I'd say that if you have a cache, keep it. If you only have haproxy, you can try with a few rules to enable very basic caching and see if that improves the situation for you. Then you'll get a better idea about what would be required in your application to deploy an advanced cache and what benefits it could bring.