Lighthttpd is the webserver which will help to increase the speed with a small memory consumption.
Now, I assume that you have already installed both apache and lighthttpd in the server.

The main thing should be noted here is we need to have 2 IP in the server so that only we can run both apache and lighthttpd in the same port.

Go to apache configuration and locate Listen directive.
Here, Add “Listen” directive to all IP addresses of the server, except the IP for lighthttpd.

Listen IP_ADDRESS1:80

Now, restart apache and then lighthttpd.
You can try to access IP in browser and make sure both are listening on port 80.