SKY DEVELOPMENT allows a maximum of 20 simultaneous MySQL connections per cPanel on shared servers. This limit can be raised for VPS, Cloud and dedicated servers.
The 20 simultaneous database connections should be sufficient. Most database connections open and close within a fraction of a second. A forum with 500 active members will rarely hit this 20 simultaneous connections.
The SQL server will timeout after 60 seconds of inactivity for Linux hosting (shared, reseller and SEO Hosting). On Windows shared hosting, the MySQL Server will timeout after 30 seconds of inactivity. VPS, Cloud and dedicated servers can have different limits.