🎓 Optimize Speed-Critical Workflows Using Parallel Processing (Fan-Out/Fan-In)

How it works

This template is a hands-on tutorial for one of the most advanced and powerful patterns in n8n: asynchronous parallel processing, also known as the Fan-Out/Fan-In model.

When should you use this?
Use this pattern when speed is your top priority and you have multiple independent, long-running tasks. Instead of running them one after another (which is slow), this workflow runs them all at the same time and waits for them all to finish.

We use a Construction Project analogy to explain the architecture:

• The Main Workflow (Top): This is the Project Manager. It defines the project, assigns all the tasks to specialist teams, and then pauses, waiting for a final report.
• The Sub-Workflow (Bottom): This represents the Specialist Teams. It's a single, reusable workflow that can perform any task it's assigned.
• Static Data (The Brains): A hidden Project Dashboard is used to track the status of every task in real-time.

The process follows three key phases:

1. Fan-Out: The Project Manager starts multiple sub-workflows at once without waiting for them to finish.
2. Asynchronous Execution: Each Specialist Team works on its task independently and in parallel. When a team finishes, it updates its status on the Project Dashboard.
3. Fan-In: The Project Manager, which has been paused by a Wait node, is only resumed when the Project Dashboard confirms that all tasks are complete. It then receives the aggregated results from all the parallel tasks.

Set up steps

Setup time: < 1 minute

This workflow is a self-contained tutorial. The only setup required is to configure the AI model.

1. Configure Credentials:
   • Go to the The AI Specialist node in the sub-workflow (bottom flow).
   • Select your desired AI credential (Gemini in that case).
2. Execute the Workflow:
   • Click the "Execute Workflow" button on the Start Project node.
3. Explore and Learn:
   • Follow the execution path to see how the main workflow fans out, and how the sub-workflow is called multiple times.
   • Click on each node and read the detailed sticky notes to understand its specific role in this advanced pattern.