PostgreSQL 18 brings several security, monitoring, and developer enhancements relevant to Amazon RDS and Aurora PostgreSQL users. Key changes include: deprecation of MD5 password authentication in favor of SCRAM-SHA-256 with a new md5_password_warnings parameter; new parallel worker tracking columns in pg_stat_database and pg_stat_statements to detect worker shortages; expanded pg_stat_subscription_stats with seven new conflict-type columns for logical replication diagnostics; automatic optimizer statistics preservation during pg_upgrade; native uuidv7() function for timestamp-ordered UUIDs that avoid B-tree index fragmentation; logical replication streaming now defaults to ‘parallel’; idle_replication_slot_timeout to auto-invalidate abandoned replication slots; COPY command gains REJECT_LIMIT and LOG_VERBOSITY silent options; and OLD/NEW aliases in RETURNING clauses for DML statements.