When Fast Failures Fool Your Metrics: Understanding Real HikariCP Performance

Performance metrics like P95 latency can be deceptive when connection pools are under stress—fast failures masquerade as fast responses. This analysis reveals why you need separate measurements for successful vs. failed queries, and provides a reproducible testing lab (hikaricp-pool-experiment) that isolates real pool behavior. For engineers tuning database connections in production systems, understanding these signal differences is critical to making correct configuration decisions.