LSAPI is the PHP mode used on servers with the LiteSpeed web server. LSAPI was designed to improve web server efficiency (up to 20% faster than FastCGI, 50% faster than mod_php and 75% faster than nginx + php-fpm bundle). At least that's what the developers assure.
In fact, these figures are probably overestimated: usually the operation of a web server depends on the environment, as well as the installed software and the characteristics of the machine. In terms of security, the mode fully supports suEXEC, which is good for shared hosting, and also allows you to install PHP in jail with user isolation.
LSAPI supports changing the PHP configuration through the control panel or through.htaccess files, and also allows you to deploy multiple PHP configurations on shared hosting, allow you to change the configuration of each virtual host regardless of the main configuration. Ruby support using persistent connections between the web server and Ruby processes allows you to implement work using a special secure protocol. In addition, the built-in process manager for Ruby allows you to control the load on the system. Also LSAPI has native Rack support.
This PHP mode has many more good features, but I will not describe all of them here. You can create your own test configuration and run the server with different loads back and forth to decide if LSAPI mode is right for you, as well as to assess its strengths and weaknesses. In my opinion, this mode is perfect for CloudLinux, since in conjunction with the lve manager it will make an excellent pair for everyday use by your hosting users. And for an ordinary user, it is not a sin to miss this opportunity.
I personally consider each PHP mode as a box that opens for everyone in different ways, which means that it can also manifest itself in different ways. I want to say one thing - do not scold LSAPI right away and evaluate its advantages and disadvantages yourself.
