> ## Documentation Index
> Fetch the complete documentation index at: https://filament.getgalaxy.io/llms.txt
> Use this file to discover all available pages before exploring further.

# AWS S3

> Write NDJSON objects to Amazon S3 or any S3-compatible endpoint.

`connectors/object` (registered as `s3`) writes each resource to its own
NDJSON object in an S3-compatible bucket, one record per line — the same
dev-readable line shape the [Stdout](/pages/connectors/sinks/stdout) sink
emits.

## Layout

A run lands one object per resource at `<prefix>/<run>/<resource>.ndjson`.

## Streaming multipart upload

S3 objects aren't appendable, so each resource streams through its own
multipart upload: `Write` buffers records into a part, and once the buffer
crosses the configured part size (default 16 MiB, 5 MiB minimum — S3's
floor for any non-final part) it's handed to a background goroutine to
upload while the next part keeps encoding. A sink-wide semaphore
(`upload_concurrency`, default 8) caps total in-flight parts across every
resource, backpressuring `Write` once the cap is hit rather than growing
unboundedly. `Commit` waits out every in-flight part, flushes each
resource's tail, and completes the multipart uploads in parallel; a
resource that produced zero records still lands as an empty object (S3
forbids a zero-part multipart upload, so that path uses a plain
`PutObject`). `Abort` cancels every in-flight upload so a failed run leaves
nothing behind.

## S3-compatible endpoints

Setting `endpoint` points the client at a non-AWS gateway (MinIO and most
others) and switches to path-style addressing automatically. Static
`access_key_id`/`secret_access_key` are optional — omitted, the sink falls
back to the AWS SDK's default credential chain.

## Modes

Supports `Append` and `SnapshotReplace` write policies (see [Replication
modes](/pages/guides/concepts/replication-modes)).