Temporal's Standalone Activities solve a classic distributed systems problem: reliably bridging Pub/Sub messages to durable execution without building custom retry logic, state tracking, and reconciliation jobs. A Standalone Activity acts as a thin, durable bridge — the event handler receives a Pub/Sub message, kicks off the Activity, and ACKs immediately. Temporal handles retries, timeouts, and visibility. Key implementation details include using deterministic Workflow IDs derived from file paths to prevent duplicate processing on retries, and setting `id_conflict_policy=USE_EXISTING` so redelivered messages attach to in-flight executions rather than spawning duplicates. Other use cases include webhooks, email sending, and external data sync — any single-function response to an external event that needs durability without a full Workflow.
