# Amazon S3 Vectors adds metadata pre‑filtering in GovCloud regions

> Amazon S3 Vectors can now pre‑filter metadata in US‑East and US‑West GovCloud, returning up to five times more matching vectors.

Oossa · 2026-10-09 · https://oossa.com/en/amazon-s3-vectors-adds-metadata-pre-filtering-in-govcloud-regions

Amazon has enabled metadata pre‑filtering for S3 Vectors in the AWS GovCloud (US‑East) and (US‑West) regions. The feature checks metadata filters before doing a similarity search, which can return up to five times more matching vectors when the filter is selective. A new $startsWith operator lets you filter on prefixes such as paths or URLs. Existing indexes can be switched to pre‑filtering with the UpdateIndexMode API, and you can test it per query before committing.

## The facts

- Available in GovCloud US‑East and US‑West as of 2026‑10‑09
- Pre‑filtering can return up to 5 × more matching vectors

## Why it matters

Government customers can retrieve more relevant results for RAG and semantic‑search workloads without changing their code.

## Sources & references

1. [Amazon S3 Vectors metadata pre-filtering is now available in AWS GovCloud (US) Regions](https://aws.amazon.com/about-aws/whats-new/2026/10/s3-vectors-metadata-pre-filtering-in-govcloud-regions/) – AWS, 2026-10-09

Last updated: 2026-10-09