Missing or ineffective indexes cause sequential scans on large tables

Missing or ineffective indexes force PostgreSQL to perform sequential scans on large tables, consuming excessive CPU and I/O resources. This degrades query performance, especially as data volume grows.

Analyze pg_stat_statements to identify slow queries with high shared_blks_read. Check for sequential scans using seq_tup_read and seq_scans. Review query EXPLAIN plans to identify missing indexes. Add appropriate indexes on frequently queried columns and JOIN/WHERE predicates. Monitor index usage after creation.