Which Reverse Proxy Server To Use For 20-30kB Static Files

What are you currently using ? I'd go with Nginx and in future Nginx Unit application server which has upcoming node.js support About — NGINX Unit which I want to eventually integrate Nginx Unit into Centmin Mod too Nginx - nginx's UNIT

So until Nginx Unit is ready, use Nginx for reverse proxy. Though Nginx Unit can sit behind a Nginx reverse proxy too Integration with NGINX — NGINX Unit

 

which benchmarks ? all benchmarks i have done show nginx was best none have shown h2o or openlitespeed beating nginx all the time. Maybe you misread the benchmarks ?

edit: or you mean SSL - HTTP/2 - h2o vs OpenLiteSpeed vs Nginx SPDY/3.1 ? diff between h2o and nginx isn't much at all if you go by numbers of page load speed and that was with nginx and deprecated spdy/3.1 and not nginx's current http/2 implementation. I'd suggest Nginx as it's more stable and well known as well as future Nginx Unit support makes transition easier.

But best to test all web server's reverse proxy implementations yourself for your own usage cases and decide as it also depends on how each are respectively configured.