Postgres 18's async I/O subsystem hits 3x on sequential scans

Postgres 18 shipped late 2025 and continues active patch releases through 2026. The headline feature is the new asynchronous I/O subsystem [Postgres 18 release notes].

── What shipped ──

The AIO subsystem lets Postgres issue multiple I/O requests concurrently rather than blocking on each one in sequence. Supported operations include:

• Sequential scans
• Bitmap heap scans
• Vacuum

Benchmarks across these workloads show up to 3x gains in certain scenarios.

Other notable additions in 18 [press kit]:

• Skip-scan lookups on multicolumn B-tree indexes for queries that omit = on prefix columns
• OR-condition index optimisation in WHERE clauses
• uuidv7() for timestamp-ordered UUIDs
• Virtual generated columns computed on read (now the default for generated columns)
• OAuth 2.0 authentication support
• OLD/NEW in RETURNING clauses for INSERT, UPDATE, DELETE, MERGE
• Temporal constraints for PRIMARY KEY, UNIQUE, FOREIGN KEY
• Statistics preserved across major-version upgrades — no more cold-start performance dip after pg_upgrade

── Why it matters ──

The AIO change is the most consequential. Postgres has been catching up on parallelism for a decade — parallel queries shipped in 9.6, parallel index builds in 11, parallel vacuum in 13. AIO closes the gap on storage-bound workloads, where Postgres has historically lagged behind systems with native async I/O.

The 3x figure is the headline; real-world gains depend on storage characteristics. Cloud-managed Postgres (RDS, Cloud SQL, Neon, Supabase) instances on NVMe-class storage will see the largest improvements. Older spinning-disk deployments will see less.

The statistics-preservation change is the underrated one. Major-version upgrades historically required ANALYZE afterwards to rebuild planner statistics, producing a known performance dip. 18 keeps statistics across the upgrade, removing that operational gotcha.

── Editor's take ──

Postgres 18 is the kind of release that makes platform engineers' lives quieter. AIO is the headline win, but the upgrade-statistics fix removes a real operational headache. If you're on 16 or 17, the 18 upgrade path is straightforward — schedule it.