Local Debugging

Lambda Web Adapter lets you develop locally with familiar tools and debuggers — just run your web app and test it directly.

Running Locally

Since the adapter only activates inside the Lambda execution environment, your app runs as a normal web server locally:

# Node.js
node index.js

# Python
uvicorn main:app --port 8080

# Java
./mvnw spring-boot:run

Simulating Lambda with SAM CLI

To simulate the full Lambda runtime environment locally, use AWS SAM CLI:

sam local start-api

Note: sam local starts a Lambda Runtime Interface Emulator on port 8080. Your web application should avoid port 8080 if you plan to use sam local. Set AWS_LWA_PORT to a different port.

Testing Individual Invocations

sam local invoke MyFunction --event event.json