Modular & Lambda Workflows

Sometimes you’ll want to reuse the same set of steps in multiple workflows.

Modular (lambda) workflows let one workflow run another workflow.

This helps you:

• Keep workflows smaller and easier to understand
• Reuse the same “module” in multiple places
• Update the module once instead of updating many workflows

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Why use modular (lambda) workflows

• Reuse logic across different workflows: for example, a “Normalize Data” or “Send Report” module.
• Keep individual workflows smaller, faster, and easier to maintain.
• Update a sub-workflow once and have multiple parent workflows benefit automatically.

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How it works

Step 1: Create the reusable workflow

• Create a new workflow as a Lambda workflow.
• Start it with a Lambda Input node and declare the inputs it expects, with their defaults.
• Build the steps, and end with a Lambda Output node that declares what it returns.

Step 2: Call it from a parent workflow

• In the parent workflow, open the node list, switch to the Customs tab and pick the workflow under My Lambda Workflows. It appears as a node named after the workflow.
• Fill its fields (one per declared input) with fixed values or expressions such as {{ $input.email }}.
• Read what it returned in the next step, for example {{ $input.summary }}.

Node reference: Lambda Workflow.

How data passes between workflows

sequenceDiagram
  participant Parent as Parent workflow
  participant Node as Lambda Workflow node
  participant In as Lambda Input
  participant Out as Lambda Output

  Parent->>Node: Item reaches the node
  Node->>In: Starts the lambda workflow with the field values
  In->>Out: The lambda's steps run
  Out-->>Node: Returns the declared values
  Node-->>Parent: Next step reads them as $input

Like most nodes, the Lambda Workflow node runs once per item it receives, so each run of the lambda workflow works on a single item. Decide what inputs the lambda expects and what it returns, and keep both small.

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Best practices

• Name sub-workflows descriptively (e.g., Normalize Data, Send Monthly Report).
• Document inputs and outputs: use Sticky Notes (see Sticky Notes) on your workflows.
• After import or copy of workflows, test parent workflows to confirm integration.
• Avoid circular calls (Workflow A calls B, and B calls A) unless intentionally designed.
• Keep sub-workflows focused on one task only: modular and reusable logic is easier to track and maintain.

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When not to use modular workflows

• The logic is very simple and used only once—modularizing may add unnecessary overhead.
• Interdependencies between actions are tightly coupled and harder to break out.
• Latency is a concern: if the parent must wait for a sub workflow that takes long, reconsider splitting. In such cases, you may prefer simpler patterns like Splitting workflows or Looping & Iteration.