Many Apache projects support interaction with a relational database. Creating a
new connection for each user can be time consuming (often requiring multiple
seconds of clock time), in order to perform a database transaction that might
take milliseconds. Opening a connection per user can be unfeasible in a
publicly-hosted Internet application where the number of simultaneous users can
be very large. Accordingly, developers often wish to share a "pool" of open
connections between all of the application's current users. The number of users
actually performing a request at any given time is usually a very small
percentage of the total number of active users, and during request processing
is the only time that a database connection is required. The application itself
logs into the DBMS, and handles any user account issues internally.