How n8n Works Internally - Architecture & Execution Engine Explained

Introduction

n8n is widely known as a low-code workflow automation tool, but most developers only interact with its UI. To build scalable, reliable, and production-ready workflows, it’s important to understand how n8n works internally - from workflow execution to data handling and persistence.

This article explains n8n’s internal architecture and execution engine in a simple yet technical way, with real-world examples.

WHAT is n8n’s Internal Architecture?

Internally, n8n is a Node.js-based workflow orchestration engine that executes workflows defined as JSON objects.

Core Internal Components

Component	Purpose
Editor UI	Visual workflow builder (frontend)
REST API	Controls workflows programmatically
Execution Engine	Runs workflows node-by-node
Node System	Modular logic units (Trigger / Action nodes)
Queue & Worker (optional)	Scales execution
Database	Stores workflows, credentials, executions

WHY Understanding n8n Internals Matters

Understanding internals helps you:

• ✅ Build optimized workflows

• ✅ Avoid performance bottlenecks

• ✅ Handle errors properly

• ✅ Scale workflows safely

• ✅ Create custom nodes

• ✅ Deploy n8n for enterprise usage

Without this knowledge, workflows may work in development but fail in production.

WHERE n8n Runs & Stores Data

Runtime Environment

n8n can run:

• Locally (Node.js)

• Docker

• Kubernetes

• Cloud VM

Database Layer

n8n stores data in:

• SQLite (default, dev)

• PostgreSQL (recommended)

• MySQL

Stored Data Includes:

• Workflows (JSON)

• Node configurations

• Credentials (encrypted)

• Execution history

WHEN the Execution Engine Is Triggered

A workflow execution starts when a Trigger Node fires.

Examples:

• Webhook receives HTTP request

• Cron schedule fires

• Polling trigger fetches new data

• Manual execution from UI

Once triggered:
➡ Execution Engine takes control
➡ Workflow is converted to an execution plan

HOW n8n Execution Engine Works (Step-by-Step)

🔹 Step 1: Workflow JSON Definition

Every workflow is stored as JSON:

{
  "nodes": [
    {
      "id": "1",
      "name": "Webhook",
      "type": "n8n-nodes-base.webhook"
    },
    {
      "id": "2",
      "name": "Set Data",
      "type": "n8n-nodes-base.set"
    }
  ],
  "connections": {
    "Webhook": {
      "main": [["Set Data"]]
    }
  }
}

Step 2: Execution Context Creation

n8n creates an Execution Context:

• Execution ID

• Input data

• Node metadata

• Run mode (manual / production)

Step 3: Node-by-Node Execution

Nodes are executed sequentially or in parallel depending on connections.

Each node:

1. Receives input data

2. Executes its logic

3. Returns output data

4. Passes data to the next node

Step 4: Data Flow Between Nodes

Data is passed as structured JSON:

[
  {
    "json": {
      "orderId": 123,
      "amount": 500
    }
  }
]

This allows:

• Transformation

• Filtering

• Branching

Step 5: Error Handling

If a node fails:

• Execution stops (default)

• Error is logged

• Error Trigger can catch failures

Example internal behavior:

try {
  executeNode();
} catch (error) {
  saveExecutionError(error);
  triggerErrorWorkflow();
}

REAL-TIME EXAMPLE: Order Processing System

Scenario

A real-time e-commerce order system using n8n.

Workflow Steps

1. Webhook receives order

2. Validate data

3. Store order in database

4. Send confirmation email

5. Notify admin on Slack

Architecture Flow

Webhook Trigger
   ↓
Validation Node
   ↓
Database Node
   ↓
Email Node
   ↓
Slack Node

Webhook Node (Sample Payload)

{
  "orderId": 789,
  "customer": "John",
  "total": 1200
}

Set Node (Data Transformation)

{
  "orderId": {{$json["orderId"]}},
  "status": "Confirmed",
  "processedAt": "{{$now}}"
}

Execution Internals

• Webhook triggers execution

• Execution ID generated

• Data flows node-to-node

• Execution stored in DB

• Status updated (Success / Failed)

Execution Modes Inside n8n

Mode	Description
Manual	Developer testing
Production	Real triggers
Queue Mode	Distributed execution
Sub-Workflow	Child execution

Queue Mode Architecture

Main n8n
  ↓
Redis Queue
  ↓
Worker n8n Instances

Used for:

• High traffic

• Parallel workflows

• Scalability

Credentials & Security Internals

• Credentials stored encrypted

• Encryption key stored as environment variable

• Never exposed in workflow JSON

N8N_ENCRYPTION_KEY=my-secret-key

Extending the Execution Engine (Custom Nodes)

Custom nodes plug into the execution engine.

Basic Node Structure

export class MyNode implements INodeType {
  execute() {
    return [
      {
        json: { message: "Hello from custom node" }
      }
    ];
  }
}

Execution Engine:

• Loads node

• Executes execute()

• Handles output

n8n is not just a visual automation tool, it’s a powerful execution engine built on Node.js with modular architecture, persistent execution tracking, and scalable processing.

Understanding its internals allows developers to:

• Build production-grade automations

• Scale safely

• Debug effectively

• Extend n8n beyond UI limits