Real-time and async
This section covers Blocks for real-time communication and background processing.
Choosing a real-time or async Block
| Block | Best for | Avoid when |
|---|---|---|
|
|
Live updates, chat, notifications, collaborative features via WebSocket |
Your use case is request/response only (no persistent connections needed) |
|
|
Long-running background tasks, event-driven processing, queue-based workloads |
The task completes in under a few seconds (handle it synchronously) |
|
|
Scheduled recurring tasks, periodic cleanup, report generation |
You need immediate execution triggered by an event (use AsyncJob) |
Realtime
Typed WebSocket pub/sub channels. Define namespaces with Zod schemas for type-safe message broadcasting. Publish messages from the server and subscribe from the client. Each namespace can have multiple channels for topic-based routing.
Locally, Realtime uses an in-process EventEmitter with a local WebSocket server. On AWS, it provisions API Gateway WebSocket APIs with DynamoDB for connection management. Best for live updates, chat, notifications, and collaborative features.
For more information, see bb-realtime on GitHub
AsyncJob
Background job processing. Submit work that runs asynchronously outside the request lifecycle. Define a handler function that processes each job payload. Jobs are fire-and-forget from the caller’s perspective with automatic retries on failure.
Locally, AsyncJob executes handlers in-process. On AWS, it provisions an SQS queue with a Lambda consumer. Best for tasks that don’t need an immediate response: sending emails, processing uploads, generating reports.
For more information, see bb-async-job on GitHub
CronJob
Scheduled task execution. Define a handler function and a cron expression or rate schedule. The handler runs automatically at the specified interval.
Locally, CronJob executes on schedule using Node.js timers. On AWS, it provisions an EventBridge rule that triggers a Lambda function. Best for periodic maintenance, batch processing, cleanup jobs, and report generation.
For more information, see bb-cron-job on GitHub
