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

# SubscriberHeartbeat

> Session schema, template 5

<div className="api-banner">
  <span className="api-protocol ws">SBE</span>
  <span className="api-detail">schema 33 · session</span>
  <span className="api-tag">template 5</span>
</div>

Keepalive from the client. Reports the latest server frame processed on this connection.

**Direction:** Client → Kraken

| ID | Field | Type | Encoding | Presence | Description |
| :- | :- | :- | :- | :- | :- |
| 1 | `sessionId` | [`SessionId`](/exchange/api-reference/sbe/session-types#sessionid) | field | required | |
| 2 | `clientTimestampNs` | [`TimestampNs`](/exchange/api-reference/sbe/session-types#timestampns) | field | required | |
| 3 | `lastReceivedServerSequence` | [`SequenceNumber`](/exchange/api-reference/sbe/session-types#sequencenumber) | field | required | Latest server frame processed on this connection |

Every message is preceded by the standard SBE `messageHeader` (`blockLength`, `templateId`, `schemaId`, `version`). See [encodings](/exchange/api-reference/sbe/session-types#messageheader).