Lambda layers for shared code in AWS - Step-by-Step Execution

Process Flow - Lambda layers for shared code

Create shared code package

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Package as Lambda Layer

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Publish Layer to AWS

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Attach Layer to Lambda function

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Invoke Lambda function

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Lambda uses shared code from Layer

This flow shows how shared code is packaged as a Lambda Layer, published, attached to a Lambda function, and then used during function execution.

Execution Sample

AWS

1. zip -r layer.zip .
2. aws lambda publish-layer-version --layer-name shared-code --zip-file fileb://layer.zip
3. aws lambda update-function-configuration --function-name MyFunction --layers <layer-arn>
4. Invoke MyFunction which uses shared code

This sequence packages shared code, publishes it as a Lambda Layer, attaches it to a Lambda function, and then runs the function using the shared code.

Process Table

Step	Action	AWS Service	Result	Notes
1	Package shared code into zip	Local	layer.zip created	Shared code ready for upload
2	Publish Lambda Layer	AWS Lambda	Layer version published	Layer ARN returned
3	Attach Layer to Lambda function	AWS Lambda	Function updated with layer	Function now uses shared code
4	Invoke Lambda function	AWS Lambda	Function runs successfully	Shared code from layer is accessible
5	Function execution ends	AWS Lambda	Execution complete	Output depends on function logic

💡 Function execution completes using shared code from attached Lambda Layer

Status Tracker

Variable	Start	After Step 1	After Step 2	After Step 3	After Step 4	Final
layer.zip	none	created	uploaded	attached	used	used
Lambda Layer ARN	none	none	generated	attached	attached	attached
Lambda Function config	no layer	no layer	no layer	layer attached	layer attached	layer attached
Function execution	not started	not started	not started	not started	running	completed

Key Moments - 3 Insights

Why do we need to package shared code into a zip file before publishing as a Lambda Layer?

AWS Lambda requires the shared code to be zipped so it can be uploaded and stored as a single artifact. This is shown in execution_table step 1 where the zip is created before publishing.

What happens if the Lambda function is not updated to include the new layer ARN?

The function will not have access to the shared code in the layer. Execution_table step 3 shows attaching the layer is necessary for the function to use the shared code.

Can multiple Lambda functions use the same layer?

Yes, once a layer is published, its ARN can be attached to multiple functions. This is implied in the flow where the layer is published once and can be reused.

Visual Quiz - 3 Questions

Look at the execution_table, at which step is the Lambda Layer ARN generated?

A Step 2

B Step 1

C Step 3

D Step 4

💡 Hint

Check the 'Result' column in execution_table for when the layer version is published.

According to variable_tracker, what is the state of the Lambda Function config after Step 3?

A No layer attached

B Layer attached

C Layer created but not attached

D Function deleted

💡 Hint

Look at the 'Lambda Function config' row under 'After Step 3' in variable_tracker.

If the shared code zip file was not created, which step in execution_table would fail?

A Step 1

B Step 3

C Step 2

D Step 4

💡 Hint

Publishing the layer requires the zip file created in Step 1, see execution_table Step 2.

Concept Snapshot

Lambda Layers let you package shared code separately.
Package shared code as a zip file.
Publish it as a Lambda Layer in AWS.
Attach the layer to your Lambda function.
Function can then use the shared code at runtime.

Full Transcript

This visual execution shows how to use Lambda Layers for shared code. First, you package your shared code into a zip file locally. Then you publish this zip as a Lambda Layer in AWS, which creates a layer version and returns an ARN. Next, you update your Lambda function configuration to attach this layer ARN. When you invoke the Lambda function, it runs and can access the shared code from the attached layer. The execution table traces each step from packaging to function execution. The variable tracker shows how key variables like the zip file, layer ARN, and function configuration change at each step. Key moments clarify why packaging is needed, the importance of attaching the layer, and that layers can be reused by multiple functions. The quiz tests understanding of when the layer ARN is generated, the function config state after attaching the layer, and what happens if the zip file is missing. The concept snapshot summarizes the process in simple steps for quick recall.