S3 and SQS Event Triggers
Learn how to trigger Lambda functions in response to Amazon S3 object events (e.g., uploads) and messages from Amazon SQS queues, facilitating data processing workflows.
S3 and SQS Event Triggers is a free Serverless AWS Lambda Development 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 Serverless AWS Lambda Development learning path, one of 4 lessons in the course, and your progress syncs across the web and the CoddyKit app.
Events Drive Serverless
Serverless functions, like AWS Lambda, don't just run on their own. They wait for something to happen! This "something" is called an event.
An event is a signal from another service that tells your Lambda function to execute. Think of it like a doorbell ringing for your function to answer.
S3 Bucket Events
Amazon S3 (Simple Storage Service) is a popular cloud storage service. It can generate events when objects are created, deleted, or modified in your buckets.
- Object Created (PUT): An image is uploaded.
- Object Deleted: A file is removed.
- Object Restored: An archived item is brought back.
These events can trigger a Lambda function to process the changes.
Connecting S3 to Lambda
To link an S3 bucket to a Lambda function, you define a trigger. This tells S3 which events to listen for and which Lambda function to invoke.
- You specify the S3 bucket.
- You choose the event types (e.g.,
s3:ObjectCreated:*). - You can filter by object prefix or suffix (e.g., only trigger for
images/folder or.jpgfiles).
What S3 Sends to Lambda
When an S3 event triggers your Lambda function, the function receives a JSON object containing details about the event. This object is the "event" parameter in your function handler.
Key information includes:
- Bucket Name: Where the event occurred.
- Object Key: The full path and name of the file affected.
- Event Name: The specific action (e.g.,
ObjectCreated:Put).
Processing an S3 Upload
Here's a Python Lambda function that processes an S3 object creation event. It extracts and prints the bucket name and the key of the uploaded object.
Try uploading a file to an S3 bucket configured to trigger this function!
import json
def lambda_handler(event, context):
for record in event['Records']:
bucket_name = record['s3']['bucket']['name']
object_key = record['s3']['object']['key']
event_name = record['eventName']
print(f"Event: {event_name}")
print(f"Bucket: {bucket_name}")
print(f"Object Key: {object_key}")
return {
'statusCode': 200,
'body': json.dumps('S3 event processed!')
}SQS Queue Messages
Amazon SQS (Simple Queue Service) is a message queuing service. It allows different parts of your application to communicate asynchronously without direct interaction.
When messages are sent to an SQS queue, they can trigger a Lambda function. This is great for tasks that can be processed later or in batches, like sending emails or processing orders.
Connecting SQS to Lambda
Setting up an SQS trigger for Lambda is straightforward. Lambda continuously polls the SQS queue for new messages.
- You specify the SQS queue.
- You define a batch size (1 to 10,000 messages). This determines how many messages Lambda tries to process in a single invocation.
- Lambda deletes messages from the queue only after successful processing.
What SQS Sends to Lambda
Similar to S3, an SQS event passed to your Lambda function is a JSON object. It contains an array of Records, each representing a message from the queue.
Each record includes:
- Message Body: The actual content of the message.
- Message Attributes: Optional metadata about the message.
- Receipt Handle: Used internally by SQS for message deletion.
Processing SQS Messages
This Python Lambda function processes messages from an SQS queue. It iterates through the batch of messages received and prints their content.
Imagine each message contains a task to perform!
import json
def lambda_handler(event, context):
for record in event['Records']:
message_body = record['body']
print(f"Received message: {message_body}")
# Add your processing logic here
return {
'statusCode': 200,
'body': json.dumps('SQS messages processed!')
}S3 vs. SQS Triggers
You've learned about two powerful event sources for AWS Lambda: S3 and SQS. They serve different purposes but both enable event-driven architectures.
Which of the following statements are TRUE regarding S3 and SQS Lambda triggers?
Recap: S3 & SQS Triggers
Great job! You've explored how AWS Lambda functions can be triggered by events from Amazon S3 and SQS.
- S3 triggers are perfect for reacting to file changes, like image uploads or document processing.
- SQS triggers enable asynchronous processing of messages, allowing for decoupled and scalable workflows.
These event sources are fundamental to building powerful, reactive serverless applications!
Frequently asked questions
Is the “S3 and SQS Event Triggers” lesson free?
Yes — the full text of “S3 and SQS Event Triggers” is free to read here on the web, and the Serverless AWS Lambda Development 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 Serverless AWS Lambda Development course, upgrade to CoddyKit PRO.
What will I learn in “S3 and SQS Event Triggers”?
Learn how to trigger Lambda functions in response to Amazon S3 object events (e.g., uploads) and messages from Amazon SQS queues, facilitating data processing workflows. You practise Serverless AWS Lambda Development 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 Serverless AWS Lambda Development?
No prior experience is required. Serverless AWS Lambda Development 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 “S3 and SQS Event Triggers” 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 Serverless AWS Lambda Development lesson?
Yes. Every Serverless AWS Lambda Development 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.