Amazon Web Services announced on October 9, 2026, that S3 Vectors metadata pre-filtering is now available in the AWS GovCloud (US-East) and AWS GovCloud (US-West) Regions.
New Features in GovCloud
According to Amazon, pre-filtering evaluates metadata filters before running similarity search, which can return up to 5x more matching vectors when a filter is selective. The update also introduces a prefix match operator, $startsWith, to filter values such as paths and URLs.
New vector buckets in AWS GovCloud (US) Regions use metadata pre-filtering by default. Amazon stated that users do not need to change how they write vectors with PutVectors or run filtered queries with QueryVectors.
Implementation and Availability
Users can update existing indexes in place using the UpdateIndexMode API. Amazon also provides a per-query parameter on QueryVectors to compare pre-filtering against current filtering before updating an index.
Metadata pre-filtering is available at no additional cost in commercial AWS Regions where Amazon S3 Vectors is available, as well as AWS China Regions, with deployment completing in the coming days.
What to do
- To use pre-filtering on an existing index, update it in place with the UpdateIndexMode API.
- Compare pre-filtering against current filtering on the same index using a per-query parameter on QueryVectors before updating.
- Get started using the AWS CLI, AWS SDKs, or the Amazon S3 console.
Key facts and where they come from
- S3 Vectors metadata pre-filtering is available in AWS GovCloud (US-East) and AWS GovCloud (US-West) Regions.
Amazon S3 Vectors metadata pre-filtering is now available in the AWS GovCloud (US-East) and AWS GovCloud (US-West) Regions.
- Pre-filtering evaluates metadata before similarity search, returning up to 5x more matching vectors when selective.
Pre-filtering evaluates metadata filters before running similarity search, returning up to 5x more of the matching vectors when your filter is selective.
- A prefix match operator ($startsWith) was added for filtering values like paths and URLs.
S3 Vectors also adds a prefix match operator ($startsWith) for filtering on values like paths and URLs.