Lambda Triggers and Integrations
Connect Lambda functions to various AWS services like S3, DynamoDB, and API Gateway to create powerful, event-driven workflows.
Lambda Triggers and Integrations is a free AWS for Backend Developers (EC2, S3, RDS, Lambda) lesson on CoddyKit — lesson 3 of 4. You can read the complete lesson below for free — then practise it hands-on in the browser with a built-in code editor and a 24/7 AI tutor. It is part of the AWS for Backend Developers (EC2, S3, RDS, Lambda) learning path, one of 4 lessons in the course, and your progress syncs across the web and the CoddyKit app.
Events Bring Lambda to Life
Welcome to the heart of serverless architecture: Lambda Triggers! These are the events that tell your Lambda function when to run. Instead of constantly running a server, your function springs into action only when needed.
Think of it like a doorbell for your code. Someone presses the button (an event occurs), and your function responds.
How Triggers Work: Push vs. Pull
Lambda triggers come in two main flavors:
- Push-based: The event source (like S3 or SNS) directly invokes your Lambda function when an event happens. Lambda receives the event and runs your code.
- Pull-based: Lambda itself polls an event source (like SQS queues or DynamoDB Streams) for new items. When new data is found, Lambda retrieves it and invokes your function.
Understanding this helps you design efficient event-driven workflows.
S3 Event Triggers: React to Storage
One of the most common and powerful triggers is Amazon S3. You can configure an S3 bucket to automatically invoke a Lambda function whenever specific events occur, such as:
- New object created (e.g., an image upload)
- Object deleted
- Object restored
This is perfect for tasks like image resizing, data validation, or generating thumbnails as soon as a file is uploaded.
S3 Trigger Demo: Logging Uploads
Here's a basic Python Lambda function that would be triggered by an S3 object creation event. It simply logs the bucket and object key from the event data.
Try running the simulated event:
import json
def lambda_handler(event, context):
"""
Simulated Lambda handler for S3 events.
Logs the details of the S3 event.
"""
print("--- S3 Event Received ---")
for record in event.get('Records', []):
bucket_name = record['s3']['bucket']['name']
object_key = record['s3']['object']['key']
event_name = record['eventName']
print(f"Bucket: {bucket_name}")
print(f"Object: {object_key}")
print(f"Event: {event_name}")
print("-------------------------")
return {
'statusCode': 200,
'body': json.dumps('S3 event logged!')
}
if __name__ == "__main__":
# Simulate an S3 PUT event
mock_event = {
"Records": [
{
"eventSource": "aws:s3",
"eventName": "ObjectCreated:Put",
"s3": {
"bucket": {"name": "my-cool-bucket"},
"object": {"key": "my-new-file.txt"}
}
}
]
}
lambda_handler(mock_event, None)DynamoDB Streams: Database Changes
Amazon DynamoDB Streams provide a time-ordered sequence of item-level modifications in a DynamoDB table. When you enable a stream, every create, update, or delete operation is captured.
Lambda can be configured to read from these streams, allowing you to react to database changes in real-time. Use cases include:
- Data replication across tables
- Auditing changes
- Triggering downstream workflows
DynamoDB Stream Demo: Processing Updates
This Python Lambda function simulates processing events from a DynamoDB Stream. It logs the event type (INSERT, MODIFY, REMOVE) and the keys/new image of the affected item.
Run it to see how a database change event looks:
import json
def lambda_handler(event, context):
"""
Simulated Lambda handler for DynamoDB Stream events.
Logs the details of the changed records.
"""
print("--- DynamoDB Stream Event Received ---")
for record in event.get('Records', []):
event_name = record['eventName']
keys = record['dynamodb']['Keys']
new_image = record['dynamodb'].get('NewImage', {})
print(f"Event: {event_name}")
print(f"Keys: {json.dumps(keys)}")
print(f"New Image: {json.dumps(new_image)}")
print("------------------------------------")
return {
'statusCode': 200,
'body': json.dumps('DynamoDB stream processed!')
}
if __name__ == "__main__":
# Simulate a DynamoDB INSERT event
mock_event = {
"Records": [
{
"eventID": "1",
"eventName": "INSERT",
"dynamodb": {
"Keys": {"id": {"S": "123"}},
"NewImage": {"id": {"S": "123"}, "name": {"S": "Alice"}},
"StreamViewType": "NEW_AND_OLD_IMAGES"
}
}
]
}
lambda_handler(mock_event, None)API Gateway: Serverless API Endpoints
Amazon API Gateway acts as a 'front door' for applications to access backend services, including Lambda functions. It handles all the tasks involved in accepting and processing up to hundreds of thousands of concurrent API calls.
By integrating API Gateway with Lambda, you can build powerful, scalable, and secure RESTful APIs without managing any servers. Users make an HTTP request, API Gateway routes it to your Lambda, and your Lambda returns a response.
API Gateway Demo: Your Serverless API
This Lambda function shows how to respond to an API Gateway request. It receives event data about the HTTP request and returns a JSON response, which API Gateway then sends back to the client.
Run the simulation to see the expected output:
import json
def lambda_handler(event, context):
"""
Simulated Lambda handler for API Gateway events.
Returns a simple JSON response.
"""
print("--- API Gateway Event Received ---")
print(f"HTTP Method: {event.get('httpMethod')}")
print(f"Path: {event.get('path')}")
print("----------------------------------")
response_body = {
"message": "Hello from your serverless API!",
"input": event
}
return {
'statusCode': 200,
'headers': {
'Content-Type': 'application/json'
},
'body': json.dumps(response_body)
}
if __name__ == "__main__":
# Simulate an API Gateway GET request event
mock_event = {
"resource": "/",
"path": "/",
"httpMethod": "GET",
"headers": {
"Accept": "text/html"
},
"queryStringParameters": None,
"pathParameters": None,
"body": None,
"isBase64Encoded": False
}
response = lambda_handler(mock_event, None)
print("\n--- API Response ---")
print(json.dumps(response, indent=2))More Powerful Integrations
Lambda can integrate with many other AWS services to build incredibly flexible architectures:
- Amazon SQS: Process messages from a queue for asynchronous tasks.
- Amazon SNS: Respond to notifications (e.g., sending emails or SMS).
- CloudWatch Events/EventBridge: Trigger Lambda functions on a schedule, or in response to AWS service events (e.g., an EC2 instance state change).
- Kinesis: Process real-time streaming data.
These integrations form the backbone of modern, event-driven applications.
Quick Check
Test your knowledge of Lambda triggers!
Recap: The Heart of Serverless Workflows
You've learned that Lambda functions are powerful, but they need triggers to come to life! These triggers are events from other AWS services that automatically invoke your function.
We explored how S3, DynamoDB Streams, and API Gateway can act as direct event sources, enabling you to build responsive, event-driven applications without managing servers. Understanding triggers is key to unlocking the full potential of serverless architecture!
Frequently asked questions
Is the “Lambda Triggers and Integrations” lesson free?
Yes — the full text of “Lambda Triggers and Integrations” is free to read here on the web, and the AWS for Backend Developers (EC2, S3, RDS, Lambda) course includes 4 lessons in total. To practise it interactively (a built-in code editor and a 24/7 AI tutor) and unlock the rest of the AWS for Backend Developers (EC2, S3, RDS, Lambda) course, upgrade to CoddyKit PRO.
What will I learn in “Lambda Triggers and Integrations”?
Connect Lambda functions to various AWS services like S3, DynamoDB, and API Gateway to create powerful, event-driven workflows. You practise AWS for Backend Developers (EC2, S3, RDS, Lambda) with hands-on code you run directly in the browser, and a 24/7 AI tutor answers your questions as you work through the lesson.
Do I need any experience to start AWS for Backend Developers (EC2, S3, RDS, Lambda)?
No prior experience is required. AWS for Backend Developers (EC2, S3, RDS, Lambda) on CoddyKit is structured for beginners through advanced learners; this is — lesson 3 of 4, so you can start here or from the beginning and move at your own pace.
How long does the “Lambda Triggers and Integrations” lesson take?
Most CoddyKit lessons take about 5–10 minutes. Each one is bite-sized and interactive, so you make steady progress and pick up exactly where you left off across the web and the app.
Can I write and run code in this AWS for Backend Developers (EC2, S3, RDS, Lambda) lesson?
Yes. Every AWS for Backend Developers (EC2, S3, RDS, Lambda) lesson includes a built-in code editor, so you write and run real code right in your browser and get instant AI feedback — no local setup required.
All lessons in this course
- What is AWS Lambda?
- Building Your First Lambda Function
- Lambda Triggers and Integrations
- Monitoring and Debugging Lambda Functions