Slow PostgreSQL queries with high execution time or IO consumption

Queries with high execution time, slow IO, or frequent invocation degrade application performance and can be identified through Heroku Data diagnostics or query plan analysis

Identify slow queries using Heroku Data's Diagnose tab (break down by slowest I/O, execution time, most frequently invoked, most time consuming). Re-run with EXPLAIN (ANALYZE, COSTS, VERBOSE, BUFFERS, FORMAT JSON) prefix. Analyze query plan with pev2 tool at explain.dalibo.com. Optimize based on plan showing costliest nodes or bad estimates.