When PostgreSQL Throughput Looks Fine but p99 Is Already Falling Apart
A PostgreSQL service can keep processing almost the same number of requests per second while its slowest requests become several times worse. CPU may still look comfortable, query execution time may barely move, and throughput may remain almost flat. The problem can appear one layer earlier, inside the connection pool, where requests start waiting before PostgreSQL even sees them. This experiment shows how that happens and why p99 usually notices it long before RPS does.



















