🛒 E-Commerce Orders API (Serverless, Python, AWS Lambda)

A lightweight, serverless Order Management API built using:

• ✅ AWS Lambda + API Gateway (REST)
• 🧰 AWS Lambda Powertools for Python (logging, tracing, metrics, idempotency, feature flags)
• 📦 DynamoDB as the order database
• 🛠️ Pydantic for request validation
• 🚀 LocalStack for local AWS emulation and testing

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📌 Features

• Create and fetch orders
• Type-safe payloads with validation using Pydantic
• Idempotent POST /order endpoint (prevents double orders)
• Feature flags controlled via AWS AppConfig
• Metrics, logs, and tracing via Powertools
• Fully local development possible with LocalStack

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🧱 Architecture

Client → API Gateway → Lambda (APIGatewayRestResolver + Pydantic)
                                   ├── DynamoDB (Orders table)
                                   ├── AWS AppConfig (feature flags)
                                   ├── AWS CloudWatch (metrics/logs)
                                   └── AWS X-Ray (tracing)

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🧰 Tech Stack

Layer	Tool / Library
API	AWS API Gateway (REST)
Function	AWS Lambda (Python 3.11)
Framework	AWS Lambda Powertools
Routing	APIGatewayRestResolver
Validation	Pydantic
Database	DynamoDB
Local Testing	LocalStack
IaC	AWS SAM

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📁 Project Structure

ecommerce-orders/
├── app.py                  # Lambda handler + routing
├── models.py               # Pydantic data models
├── requirements.txt
├── utils/
│   ├── db.py               # DynamoDB helpers
│   └── features.py         # Feature flags
├── template.yaml           # AWS SAM template
└── README.md

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🚀 Getting Started

1. Install Tools

Make sure you have the following installed:

• 🐍 Python 3.11+
• 🐳 Docker (for LocalStack)
• 📦 AWS CLI
• 📦 AWS SAM CLI → https://docs.aws.amazon.com/serverless-application-model/latest/developerguide/install-sam-cli.html
• 📦 LocalStack → https://docs.localstack.cloud/getting-started/installation/

Install Python dependencies:

pip install -r requirements.txt

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2. Run Locally with LocalStack

Start LocalStack:

localstack start -d

Create DynamoDB Table:

awslocal dynamodb create-table   --table-name Orders   --attribute-definitions AttributeName=order_id,AttributeType=S   --key-schema AttributeName=order_id,KeyType=HASH   --billing-mode PAY_PER_REQUEST

Deploy Lambda Function (SAM + LocalStack):

sam build
AWS_ENDPOINT_URL=http://localhost:4566 sam deploy --guided   --parameter-overrides "Environment=local"

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3. Usage

POST /order

Creates an order.

curl -X POST http://localhost:4566/restapis/{api_id}/local/_user_request_/order   -H "Content-Type: application/json"   -d '{"customer": "John Doe", "items": ["item1", "item2"]}'

GET /order/{order_id}

Fetch a specific order:

curl http://localhost:4566/restapis/{api_id}/local/_user_request_/order/{order_id}

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⚙️ Environment Variables

These are used internally by Powertools:

POWERTOOLS_SERVICE_NAME=orders
POWERTOOLS_METRICS_NAMESPACE=EcommerceApp

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🧠 Developer Notes

Powertools Modules Used:

• Logger: structured logging
• Tracer: distributed tracing via AWS X-Ray
• Metrics: custom CloudWatch metrics
• Idempotency: safely retryable functions
• Feature Flags: staged rollouts

Advanced Enhancements (TODO):

• SQS integration for async processing
• Add JWT-based auth (Cognito/JWT + Lambda Authorizer)
• Pagination and filters on GET /order
• GitHub Actions CI/CD

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📚 References

• 📖 AWS Lambda Powertools Docs
• 📖 LocalStack Docs
• 📖 SAM CLI Docs

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📄 License

MIT License - feel free to fork, improve, and reuse!