# Firehose — Amazon Data Firehose

Delivery streams exist as records and accept writes, but there is no delivery:
every record is acknowledged and discarded.

**Status:** ⚠️ Partial

## Quick start

```bash
export AWS_ENDPOINT_URL=http://localhost:4566

aws firehose create-delivery-stream --delivery-stream-name events
aws firehose put-record \
  --delivery-stream-name events \
  --record Data="$(printf 'hello' | base64)"
# → { "RecordId": "…", "Encrypted": false }
```

Any credentials work; with none configured, run `eval "$(overcast env)"` first
— see [Using AWS SDKs and CLI](/docs/sdk-cli/index.md#credentials).

## What works

| Area | Behaviour |
| --- | --- |
| Delivery streams | Create, describe, list and delete; `ACTIVE` the moment they are created |
| Stream type | `DeliveryStreamType` is honoured, defaulting to `DirectPut` |
| Writes | `PutRecord` and `PutRecordBatch` return a record id per record and `FailedPutCount: 0` |
| Tags | Inline `Tags` at creation, plus `TagDeliveryStream`, `UntagDeliveryStream` and `ListTagsForDeliveryStream` |
| Limits | Stream names, the 1,000 KiB record cap and `PutRecordBatch`'s 1–500 records / 4 MiB per call are enforced |
| Errors | A repeated stream name is `ResourceInUseException`; every exception is HTTP 400, as AWS documents |

## Differences from AWS

| Area                      | On AWS                                                                     | Overcast                                                                                                                            |
| --- | --- | --- |
| Delivery | Records reach S3, Redshift, OpenSearch or an HTTP endpoint | Records are discarded — a bucket wired as a destination stays empty |
| Destination configuration | Stored and returned | `S3DestinationConfiguration` and its siblings are ignored, and `DescribeDeliveryStream` always reports an empty `Destinations` list |
| Transformation | Lambda processors, dynamic partitioning, format conversion and compression | None of it is applied |
| Buffering | A buffer interval and size govern the flush | There is no buffer interval or size, so nothing is ever flushed |
| `UpdateDestination` | Changes a live stream's destination | Not implemented |

## Gotchas

> [!WARNING]
> A test that writes to Firehose and then asserts on objects in the
> destination bucket will never pass here. Write to [S3](/docs/services/s3/index.md) directly, or
> use [Kinesis](/docs/services/kinesis/index.md), whose records are really stored and readable.

<!-- BEGIN overcast:capabilities -->

## Operations

All 9 listed operations are implemented.
Per-operation status, notes and AWS API links: [Firehose operations](/docs/services/firehose/operations/index.md).

<!-- END overcast:capabilities -->

## Related

- [Kinesis Data Streams](/docs/services/kinesis/index.md)
- [All service pages](/docs/services/index.md)
- [Service names and state overrides](/docs/configuration/index.md#service-names)
- [AWS API reference](https://docs.aws.amazon.com/firehose/latest/APIReference/)