Understanding Lambda Runtime & Layers
Explore different Lambda runtimes and leverage Lambda Layers to manage common dependencies, libraries, and custom runtimes efficiently.
Understanding Lambda Runtime & Layers is a free Serverless AWS Lambda Development lesson on CoddyKit — lesson 1 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.
What are Lambda Runtimes?
When you write an AWS Lambda function, you need to choose a runtime. Think of a runtime as the specific language environment your code will run in.
It's like picking which kitchen your recipe will be cooked in – a Python kitchen, a Node.js kitchen, a Java kitchen, etc. AWS Lambda provides managed runtimes for popular languages.
Why Runtimes are Key
The runtime you select dictates how your code is executed, what libraries are available by default, and how your function interacts with the Lambda environment.
- Language Support: Ensures your code runs correctly.
- Dependencies: Determines pre-installed libraries.
- Performance: Different runtimes have varying startup times and execution speeds.
- Tooling: Influences the development tools you'll use.
Popular Runtimes for Lambda
AWS Lambda supports several popular programming languages out-of-the-box. Here are some of the most common ones:
- Node.js: Great for web services and event-driven apps.
- Python: Popular for scripting, data processing, and AI/ML.
- Java: Often used for enterprise applications.
- C# (.NET): For developers working in the Microsoft ecosystem.
- Go: Known for high performance and concurrency.
- Ruby: For developers who prefer its elegance and productivity.
Your First Python Lambda
Let's see a simple Lambda function written in Python. This function acts as an entry point, processing an event and returning a response.
Try running this example:
def lambda_handler(event, context):
# 'event' contains data from the trigger
# 'context' provides runtime information
name = event.get('name', 'World') # Get name from event, default to 'World'
message = f"Hello, {name}! This is your first Python Lambda."
print(message)
return {
'statusCode': 200,
'body': message
}Introducing Lambda Layers
As your Lambda applications grow, you'll often have common code, libraries, or dependencies shared across multiple functions. This is where Lambda Layers come in!
A Layer is a .zip file archive that can contain libraries, a custom runtime, or other dependencies. You can attach up to 5 layers to a Lambda function.
Benefits of Using Layers
Layers help you manage your Lambda functions more efficiently and keep them organized:
- Smaller Deployment Packages: Your function code only contains unique logic, not common libraries.
- Faster Deployments: Smaller packages upload quicker.
- Dependency Management: Update a library in one layer, and all associated functions benefit.
- Code Reusability: Share utility functions or configurations across many Lambdas.
- Separation of Concerns: Keep your business logic separate from common dependencies.
How Layers are Structured
For Lambda to find your layer content, it needs to be organized in specific folders within the .zip file. For Python, your code should be in a python/ directory.
For example, if you have a utility module called my_utils.py, your layer .zip file would look like this:
my_layer.zippython/my_utils.py
Other runtimes have similar conventions (e.g., nodejs/node_modules for Node.js).
Creating a Simple Layer
Imagine we have a common utility function that simply reverses a string. We can put this in a layer.
This would be the content of our my_utils.py file, which would then be zipped into a layer:
# my_utils.py (inside the 'python/' directory of your layer)
def reverse_string(s):
return s[::-1]
def greet_user(name):
return f"Hello, {name}!"Using a Layer in Your Lambda
Once you've created and attached a layer to your Lambda function, you can import its modules just like any other local module. Here's how our Python Lambda would use the my_utils layer:
import my_utils # This import works because 'my_utils' is in an attached layer
def lambda_handler(event, context):
input_name = event.get('name', 'there')
# Use functions from the layer
greeting = my_utils.greet_user(input_name)
reversed_greeting = my_utils.reverse_string(greeting)
print(f"Original: {greeting}")
print(f"Reversed: {reversed_greeting}")
return {
'statusCode': 200,
'body': reversed_greeting
}Quick Check on Runtimes & Layers
Which of the following is a primary benefit of using AWS Lambda Layers?
Recap & Next Steps
Great job! You've learned about Lambda runtimes and layers.
- Runtimes define the language environment for your Lambda code.
- Layers help you manage common dependencies and share code, leading to smaller, more efficient deployment packages.
By using layers, you can keep your Lambda functions lean, making them easier to deploy and maintain. Next, we'll dive into another crucial aspect of Lambda management: Environment Variables!
Frequently asked questions
Is the “Understanding Lambda Runtime & Layers” lesson free?
Yes — the full text of “Understanding Lambda Runtime & Layers” 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 “Understanding Lambda Runtime & Layers”?
Explore different Lambda runtimes and leverage Lambda Layers to manage common dependencies, libraries, and custom runtimes efficiently. 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 1 of 4, so you can start here or from the beginning and move at your own pace.
How long does the “Understanding Lambda Runtime & Layers” 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.
All lessons in this course
- Understanding Lambda Runtime & Layers
- Environment Variables and Configuration
- IAM Roles for Lambda Security
- Versioning and Aliases for Safe Releases