Well, it depends on quite a few things, but let’s start by looking at some server settings and example web applications.
Arguably the two most important settings that govern how much simultaneous traffic a Linux server running the LAMP stack can handle are the Apache MaxClients setting and the MySQL/Mariadb max_connections setting. From here on I’ll refer to both of these settings as your max connection settings. If set too high your web and database software can consume all of a server’s available memory and crash it, which can be very painful. If set too low your web server will slow incoming traffic unnecessarily.
For example, if your application is streamlined and doesn’t use much RAM to render web pages then your max connections settings can be set very high, allowing hundreds of simultaneous users to your site on a small VPS with, say, 2GB RAM. However, a WordPress site with tons of plugins – some poorly coded with non-optimized MySQL queries – can use so much RAM that the max connections settings should be set very low, in order to prevent RAM swapping and server crashes.
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