lightweight connection pooler for PostgreSQL

 PgBouncer is a lightweight connection pooler for PostgreSQL providing the
 following features:
 .
  * Several different methods of pooling connections: session pooling,
    transaction pooling, statement pooling.
  * Low memory requirements.
  * It is not tied to one backend server, the destination databases
    can reside on different hosts.
  * Supports online reconfiguration for most of the settings.
  * Supports online restart/upgrade.