Unboxing S3 Object Lambda

Michael Wittig – 05 May 2021

Amazon S3 Object Lambda offers a way to execute a Lambda function when someone wants to download a file (GetObject) from an S3 bucket. You can implement whatever logic you wish and return any data as the response via the WriteGetObjectResponse API. Keep in mind that the Lambda function must finish within 60 seconds and is called synchronously.

Unboxing S3 Object Lambda

Our unboxing series gives a first insight into new services or features. An unboxing is not as detailed as a service review.

How S3 Object Lambda works

The following figure shows the needed components:

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S3 Object Lambda

Let’s look at the parts more closely:

  • S3 Object Lamda Access Point: References your Lambda function and your S3 Access Point. Block Public Access is always enabled.
  • Lambda function: Invoked when a GetObject request is made to the S3 Object Lambda Access Point.
  • S3 Access Point: Takes care of the non GetObject requests (such as ListObjects) and serves the pre-signed URL of the original file passed into the Lambda function.
  • S3 Bucket: Stores the original file (in fact, the original file could be non-existent).

In the following video, I go into more details and share code with you:

  • Introducing S3 Object Lambda
  • Use Cases
  • Demo: Generating content
  • Understanding Pricing
  • Pitfall: Keep the Lambda function running


You pay for the following:

  • S3 Get Object API (as usual)
  • Lambda invocation
  • Lambda GB-second
  • $0.005 per GB returned via WriteGetObjectResponse
Michael Wittig

Michael Wittig

I launched cloudonaut.io in 2015 with my brother Andreas. Since then, we have published hundreds of articles, podcast episodes, and videos. It’s all free and means a lot of work in our spare time. We enjoy sharing our AWS knowledge with you.
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