System Workflow

FastAPI → Temporal Workflow → Worker → External “services” (activities)

Temporal E-Commerce Workflow Demo

This project demonstrates a real-world Temporal workflow integration using:

• FastAPI → API layer
• Temporal → workflow orchestration
• Worker → executes activities
• Docker Compose → runs Temporal infrastructure
• Order workflow → Payment → Inventory → Shipping → Email

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FULL RUN COMMANDS (END-TO-END)

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Step 1: Start Temporal Infrastructure

Run Temporal server + UI + PostgreSQL:

docker compose up -d

Verify containers:

docker ps

You should see:

• temporal
• temporal-ui
• postgres

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Step 2: Create Python Virtual Environment

Windows

python -m venv venv
venv\Scripts\activate

Linux/macOS

python3 -m venv venv
source venv/bin/activate

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Step 3: Install Dependencies

pip install -r requirements.txt

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Step 4: Start Temporal Worker

This worker executes workflow activities.

python app/worker.py

Expected output:

Worker running...

Keep this terminal running.

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Step 5: Start FastAPI Application

Open a new terminal:

 uvicorn api:app --reload

OR

uvicorn app.api:app --reload --port 8000

Expected output:

Uvicorn running on http://127.0.0.1:8000

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Workflow Testing

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Create Order Workflow

Trigger workflow via API:

curl -X POST http://localhost:8000/order/101

Response:

{
  "message": "order_started",
  "workflow_id": "order-101",
  "order_id": "101"
}

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Check Order Status

curl http://localhost:8000/order/101

While workflow is running:

{
  "status": "running"
}

After completion:

{
  "status": "completed",
  "result": {
    "order_id": "101",
    "payment": "payment_success:101",
    "inventory": "inventory_reserved:101",
    "shipping": "shipment_created:101",
    "email": "email_sent:101",
    "status": "COMPLETED"
  }
}

---

Temporal UI

Open:

http://localhost:8080

You’ll see:

• Workflow ID → order-101
• Workflow status
• Activity execution logs
• Full event history
• Retry attempts (if failures happen)

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End-to-End Workflow Flow

User/API Request
       ↓
FastAPI receives order request
       ↓
Temporal starts workflow
       ↓
Worker picks task from queue
       ↓
process_payment()
       ↓
reserve_inventory()
       ↓
create_shipping()
       ↓
send_email()
       ↓
Workflow completed
       ↓
Status visible in API + Temporal UI

---

Stop Everything

Stop FastAPI:

CTRL + C

Stop Worker:

CTRL + C

Stop Docker services:

docker compose down

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Restart Fresh

docker compose down
docker compose up -d
python app/worker.py
uvicorn app.api:app --reload --port 8000

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Common Issues

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Port already in use

Check:

netstat -ano | findstr :8000

Kill process if needed.

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Temporal UI empty

Make sure:

• Worker is running
• API triggered workflow
• Task queue names match

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Docker issues

Check logs:

docker logs temporal

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Real-World Use Cases

This same architecture can be extended for:

• E-commerce orders
• Payment processing
• Loan approval systems
• CI/CD deployment orchestration
• Ride booking systems
• Subscription billing workflows

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Future Improvements

• Add retry policies
• Add rollback workflows (Saga pattern)
• Replace mock activities with real microservices
• Add Prometheus/Grafana monitoring