POST
/
streams
/
{stream}
/
records
Append records.
curl --request POST \
  --url https://{basin}.b.aws.s2.dev/v1/streams/{stream}/records \
  --header 'Authorization: Bearer <token>' \
  --header 'Content-Type: application/json' \
  --data '{
  "records": [
    {
      "body": "<string>",
      "headers": [
        [
          "<string>"
        ]
      ],
      "timestamp": null
    }
  ]
}'
{
  "end": {
    "seq_num": 1,
    "timestamp": 1
  },
  "start": {
    "seq_num": 1,
    "timestamp": 1
  },
  "tail": {
    "seq_num": 1,
    "timestamp": 1
  }
}
Appends execute atomically — either all the records in a batch will become durable, or none. S2 returns the range of sequence numbers assigned, the timestamps of the first and last record, and the current tail. With an AppendSession (available via most SDKs), you can pipeline batches with an ordering guarantee, and receive acknowledgements back in the corresponding order. If any batch fails, subsequent batches will not become durable.
Acknowledgment latency depends on the storage class for the stream. A Standard stream will acknowledge writes within 500 milliseconds, and an Express stream within 50 milliseconds.

​
Concurrency control

Appends support two mechanisms for concurrency control:

​
Match sequence

Specifying expected current state allows optimistic concurrency control. You can provide the sequence number that you expect S2 to assign to the first record in a batch as the match_seq_num. If it does not match, this will result in a 412 Precondition Failed status or corresponding SDK error type.

​
Fencing token

Fencing is a form of pessimistic concurrency control. It is a cooperative mechanism, so an append that does not specify a fencing token will still be allowed. When an append does include a fencing_token and it does not match, this results in a 412 Precondition Failed status or corresponding SDK error type. Setting the current fencing token itself requires appending to the stream, with the fence command.

Authorizations

​
Authorization
string
header
required

Bearer authentication header of the form Bearer <token>, where <token> is your access token.

Headers

​
s2-format
enum<string>

Defines the interpretation of record data (header name, header value, and body) with the JSON content type. Use raw (default) for efficient transmission and storage of Unicode data — storage will be in UTF-8. Use base64 for safe transmission with efficient storage of binary data.

Available options:
raw,
base64

Path Parameters

​
stream
string
required

Stream name.

Body

application/json

Payload of an append request.

​
records
object[]
required

Batch of records to append atomically, which must contain at least one record, and no more than 1000. The total size of a batch of records may not exceed 1 MiB of metered bytes.

​
fencing_token
string | null

Enforce a fencing token, which starts out as an empty string that can be overridden by a fence command record.

​
match_seq_num
integer | null

Enforce that the sequence number assigned to the first record matches.

Required range: x >= 0

Response

Success response to an append request.

​
end
object
required

Sequence number of the last record that was appended + 1, and timestamp of the last record that was appended. The difference between end.seq_num and start.seq_num will be the number of records appended.

​
start
object
required

Sequence number and timestamp of the first record that was appended.

​
tail
object
required

Sequence number that will be assigned to the next record on the stream, and timestamp of the last record on the stream. This can be greater than the end position in case of concurrent appends.