You are testing a mission-critical database for a financial institution. During the test, you observe that the database response time significantly increases as the number of concurrent users grows. Which type of testing should you perform to address this issue?

Performance testing is conducted to evaluate the system's performance under various workloads. Stress testing, a subset of performance testing, specifically checks the system's response under extreme conditions, such as high loads or concurrent users. In this scenario, the observed issue suggests a need for performance testing, particularly stress testing, to identify and address the performance degradation under heavy concurrent usage.