Have you worked with PgBouncer or PgPool? What are they used for?

PgBouncer and PgPool are connection poolers for PostgreSQL that help efficiently manage database connections.

PgBouncer is a lightweight connection pooler. It supports several modes of operation, such as session pooling and transaction pooling. Its main task is to reduce the overhead of establishing connections, which improves performance with a large number of short queries.

PgPool is a more functional proxy that, in addition to connection pooling, can perform load balancing, replication, automatic failover, and query caching.

They are used for:

• Reducing the load on the database server.
• Decreasing application response times.
• Increasing fault tolerance and scalability.

For example, in high-load systems, instead of each client opening its own connection to PostgreSQL, they connect to PgBouncer, which manages the connection pool to the database.