This talk addresses a common misconception in Oracle application development: that larger connection pools in the backend automatically lead to better performance.
While this belief is widespread, experienced DBAs understand that oversized connection pools can actually harm performance.
The presentation provides an introduction to connection pool sizing for backend developers of all seniority levels, explaining the reasons why excessively large pools negatively impact system throughput and resource efficiency.

A key part of the discussion focuses on mathematical principles behind connection pool behavior, including Kingman's law, which models queueing delays,
to illustrate how adding more connections can increase waiting times rather than reduce them.
The talk also covers the mathematical foundations for sizing connection pools optimally based on workload and resource constraints.

By the end of the session, attendees will be equipped with practical formulas and guidelines to calculate the appropriate size for their connection pools.
This knowledge will enable them to guide application teams towards resizing their pools in a way that maximizes performance, stability, and efficient resource use,
rather than simply increasing pool size in hopes of improving it.

Devoxx

A talk transcript covering database connection pool sizing from first principles. Explains why opening connections is expensive (7-8 network round trips, 5ms to 1.5s depending on network distance), how connection pools work, and how to size them correctly. Applies Little's Law to calculate minimum required connections (throughput × average query time) and Kingman's Law to explain why utilization above 75-80% causes exponential wait time increases. Provides a formula for maximum pool size: (CPU cores × 2) + spindle count. Includes a real-world banking system case study showing 640 configured connections vs. the ~200 actually needed. Also covers application-side vs. database-side pools (e.g., PgBouncer), context switching overhead from oversized pools, and separating short vs. long-running workloads into different pools.

Database Connection Pool Sizing - Demystified! by Jasmin Fluri