Connection pooling is a technique used to reduce the overhead of opening and closing database connections by maintaining a pool of open connections that can be reused as needed. This approach helps improve application performance, especially at scale, by minimizing the expense of constantly opening and closing new connections. However, determining the optimal size for a connection pool requires considering various factors such as application interactions with the database, frequency of operations, database technology, hardware specifications, network latency, and more. CockroachDB recommends setting the maximum number of connections to be between 2x and 4x the number of CPU cores in your cluster for most workloads.