Amazon S3 Vectors

The Amazon S3 Vectors Embedding Store integrates with Amazon S3 Vectors, a purpose-built vector storage capability within Amazon S3 designed for storing and querying vector embeddings at scale.

Maven Dependency

<dependency>
    <groupId>dev.langchain4j</groupId>
    <artifactId>langchain4j-community-s3-vectors</artifactId>
    <version>${latest version here}</version>
</dependency>

APIs

• S3VectorsEmbeddingStore

Features

• Store embeddings with metadata
• Vector similarity search with cosine or euclidean distance
• Filter search results by metadata fields
• Automatic index creation on first embedding insertion
• Standard AWS credential provider support

Usage

Basic Configuration

S3VectorsEmbeddingStore embeddingStore = S3VectorsEmbeddingStore.builder()
    .vectorBucketName("my-vector-bucket")       // S3 Vectors bucket name (required)
    .indexName("my-index")                       // Index name within the bucket (required)
    .region("us-west-2")                         // AWS region (default: us-east-1)
    .distanceMetric(DistanceMetric.COSINE)       // Distance metric (default: COSINE)
    .createIndexIfNotExists(true)                // Auto-create index (default: true)
    .timeout(Duration.ofSeconds(60))             // API call timeout (default: 30 seconds)
    .credentialsProvider(myCredentialsProvider)  // Custom AWS credentials
    .build();

Using an Existing S3VectorsClient

If you already have a configured S3VectorsClient, you can pass it directly to the builder:

S3VectorsClient customClient = S3VectorsClient.builder()
    .region(Region.US_WEST_2)
    .credentialsProvider(myCredentialsProvider)
    .build();

S3VectorsEmbeddingStore embeddingStore = S3VectorsEmbeddingStore.builder()
    .s3VectorsClient(customClient)
    .vectorBucketName("my-vector-bucket")
    .indexName("my-index")
    .build();

Distance Metrics

S3 Vectors embedding store supports two distance metrics. The distance values are automatically converted to relevance scores in the range [0, 1], where 1 represents the most relevant match.

Cosine Distance (Default)

Best for: Text embeddings, semantic similarity search

• Measures the cosine of the angle between vectors
• Converted to relevance score: score = (1 - distance + 1) / 2
• Results are independent of vector magnitude

.distanceMetric(DistanceMetric.COSINE)  // Default, recommended for text embeddings

Euclidean Distance

Best for: When both direction and magnitude matter

• Measures straight-line distance between vectors
• Range: [0, ∞)
• Converted to relevance score: score = 1 / (1 + distance)

.distanceMetric(DistanceMetric.EUCLIDEAN)

Filtering

S3 Vectors embedding store supports filtering search results by metadata fields.

Supported Filter Operations

• isEqualTo: Equal comparison
• isNotEqualTo: Not equal comparison
• isGreaterThan: Greater than comparison
• isGreaterThanOrEqualTo: Greater than or equal comparison
• isLessThan: Less than comparison
• isLessThanOrEqualTo: Less than or equal comparison
• isIn: IN operator (multiple values)
• isNotIn: NOT IN operator
• And: Logical AND
• Or: Logical OR
• Not: Logical NOT

Implementation Details

Credentials

By default, the store uses DefaultCredentialsProvider which follows the standard AWS credential resolution chain (environment variables, system properties, credential files, EC2 instance profile, etc.). You can provide a custom AwsCredentialsProvider via the builder.

Index Creation

When createIndexIfNotExists is set to true (default), the index is created automatically on the first embedding insertion. The index dimension and distance metric are set based on the first embedding added and the configured distance metric.

Resource Cleanup

S3VectorsEmbeddingStore implements AutoCloseable. When you're done using the store, call close() to release the underlying S3VectorsClient resources, or use try-with-resources.

Limitations

• Maximum Results: S3 Vectors limits search results to 100 per query (topK range: 1-100)
• Remove by Filter: removeAll(Filter) is not supported; use removeAll(Collection<String> ids) instead
• Remove All: removeAll() deletes the entire index

Examples

• S3VectorsEmbeddingStoreIT