InterviewsVector

PostgreSQL 18 lands an asynchronous I/O subsystem

PG18's new async I/O subsystem shows up to 3× faster reads from storage, alongside virtual generated columns and a native UUIDv7 function.

What happened

PostgreSQL 18 was released on 25 September 2025 with a new asynchronous I/O (AIO) subsystem that the project reports delivering up to 3× performance improvements when reading from storage. The release also adds virtual generated columns, a native uuidv7() function, and carries planner statistics across major-version upgrades.

Why it matters

I/O is where most database performance actually lives. An async I/O engine lets Postgres overlap storage waits with useful work — meaningful for read-heavy and analytical workloads — and timestamp-ordered UUIDv7 removes a common index-fragmentation footgun for distributed key generation.

Staff engineer take

'Up to 3×' is a ceiling, not a promise — the win depends on your storage and access patterns. The Staff move is to benchmark AIO on your real workload, and to treat UUIDv7 as the new default for surrogate keys where you need sortable, index-friendly identifiers.

Interview connection

Why can asynchronous I/O improve database read throughput, and why does a UUIDv7 index better than a fully random UUID?

Probes storage-engine and indexing fundamentals.