How does max connections work internally in MySQL?

Max connections in MySQL defines the maximum number of simultaneous client connections to the MySQL server. This setting helps manage server resources and prevents overload. When the number of client connections exceeds this limit, new connection attempts are denied until existing connections are closed. The default value is usually 151, but it can be adjusted based on server capabilities and workload requirements.

Internally, MySQL maintains a connection pool. Each connection consumes RAM and CPU resources, so careful monitoring of the max connections setting is essential to ensure optimal performance. The server tracks active connections using various background processes to ensure that resources are allocated efficiently.

When a connection is attempted, MySQL checks the current number of active connections against the max connections limit. If the limit has been reached, clients receive an error message indicating that the server cannot accommodate more connections at that time.

To change the max connections setting, you can edit the MySQL configuration file (my.cnf or my.ini) or use the following SQL command: