Several applications, several databases.
THE PRINCIPLE
One database and one database user per application, with privileges only on that database.
WHY
A shared user with access to everything means one application's SQL injection exposes all of them.
It also makes backups, restores and migrations independent. Restoring one application does not affect another.
NAMING
Use a convention making the owner obvious. With the cPanel prefix, something like username_shopdb and username_shopuser.
Keep a note of which application uses which, since prefixed names become hard to distinguish at a dozen databases.
PLAN LIMITS
Shared plans limit the number of databases. Check before building something that needs many.
CONNECTION MANAGEMENT
Each application holds connections. Several applications on one account can exhaust limits.
Close connections properly and avoid opening them unnecessarily.
CROSS-DATABASE QUERIES
Possible where the user has access to both, and usually a sign the data model needs rethinking. It also couples applications that should be independent.
