If your service requires scaling because it's expensive dynamic content, then apache could easily be fast enough and not the bottleneck requiring a switch to so

If your service requires scaling because it's expensive dynamic content, then apache could easily be fast enough and not the bottleneck requiring a switch to something else. It doesn't matter if nginx/whatever can handle 1000+ reqs/sec if your app consumes 300MB of ram per request and takes 1 second to process.