Easiest Way to use an Amazon S3 trigger to invoke a Lambda function – 2023

Abhishek Sharma

9 months ago

Hey guys, in today’s blog we will see how we can use an AWS S3 trigger to invoke a Lambda function. So without any further due, let’s dive into it…

Table of Contents

Step 1 – Create an Amazon S3 Bucket.

Open your AWS Console and search for S3.
When you open S3, click on Create Bucket.

In the next step, simply name your S3 bucket, scroll down and click on Create Bucket. Keep everything else on default.
As you can see below I named my S3 bucket demo-bucket-v3.

Step 2 – Create a Lambda function.

Open your AWS Console and search for Lambda.
When you open Lambda, click on Create Function.
In the next step, name your Lambda, and choose a runtime (I selected Python 3.9).
Scroll down and click on Create function.

Step 3 – Adding Amazon S3 trigger to invoke a Lambda function.

When you have successfully created a Lambda function, you will see a screen like this.

Click on Add trigger.
On the next screen search for S3, and select the bucket you created in Step 1.

Keep everything else on default, scroll down and click on Add.

Step 4 – Give appropriate permissions to Lambda IAM Role.

Although this process is not mandatory but to be on the safer side, do this step.

On your Lambda page click on Configuration and then go to Permissions.
Then click on the Role name.
In my case it’s test-lambda-role-9etv0r1m.

Click on Add Policies, and Attach Policies.

On the next screen search for these 3 policies and attach them.

Step 5 – Testing our Trigger.

Simply upload some files to your bucket.
Then open your Lambda function’s Cloudwatch logs (Monitor -> View Logs in Cloudwatch) and see if logs are created.