What is a Temporal Activity?

This guide provides a comprehensive overview of Temporal Activities including Activity Definition, Activity Type, Activity Execution, Standalone Activity, and Local Activity.

An Activity is a normal function or method that executes a single, well-defined action (either short or long running), such as calling another service, transcoding a media file, or sending an email message. Activity code can be non-deterministic. We recommend that it be idempotent.

Activities are the most common Temporal primitive and encompass small units of work such as:

• Single write operations, like updating user information or submitting a credit card payment
• Batches of similar writes, like creating multiple orders or sending multiple messages
• One or more read operations followed by a write operation, like checking an product status and user address before updating an order status
• A read that should be memoized, like an LLM call, a large download, or a slow-polling read

Larger pieces of functionality should be broken up into multiple activities. This makes it easier to do failure recovery, have short timeouts, and be idempotent.

Workflow code orchestrates the execution of Activities, persisting the results. If an Activity Execution fails, any future attempt will start from the initial state, unless your code uses (Heartbeat details payloads) for checkpointing (storing state on the server, and using it when resuming subsequent attempts).

Activity Functions are executed by Worker Processes. When the Activity Function returns, the Worker sends the results back to the Temporal Service as part of the ActivityTaskCompleted Event. The Event is added to the Workflow Execution's Event History. For other Activity-related Events, see Activity Events.

If you only want to execute one Activity Function, then you don't need to use a Workflow: you can use your SDK Client to invoke it directly as a Standalone Activity.