Staging variables in AWS Lambda functions are a powerful feature used in conjunction with Amazon API Gateway to manage different deployment stages of your application. They allow you to configure environment-specific values that can be passed to your Lambda functions based on the current deployment…Staging variables in AWS Lambda functions are a powerful feature used in conjunction with Amazon API Gateway to manage different deployment stages of your application. They allow you to configure environment-specific values that can be passed to your Lambda functions based on the current deployment stage (such as dev, staging, or production).
When you create an API Gateway, you can define multiple stages representing different environments. Each stage can have its own set of stage variables - key-value pairs that act as configuration parameters. These variables enable you to point different stages to different Lambda function versions or aliases.
For example, you might have a Lambda function with multiple versions. Using stage variables, your development stage could invoke version 1 of your function, while production invokes version 5. This is accomplished by referencing the stage variable in your Lambda integration URI using the syntax ${stageVariables.variableName}.
Common use cases for staging variables include:
1. Pointing to different Lambda function aliases (dev, test, prod)
2. Passing configuration data like database connection strings
3. Specifying different backend endpoints per environment
4. Managing feature flags across stages
To implement staging variables, you first create them in the API Gateway console under your stage settings. Then, in your Lambda integration, you reference them using the ${stageVariables.name} syntax. Your Lambda function can access these values through the event object passed by API Gateway.
Best practices include using Lambda aliases in combination with stage variables for safer deployments, implementing proper IAM permissions for each stage, and maintaining consistent naming conventions across environments.
Staging variables provide flexibility in managing multiple environments from a single API Gateway configuration, reducing the need for duplicate resources and simplifying the deployment pipeline. They are essential for implementing blue-green deployments and canary releases in serverless architectures.
Staging Variables in Lambda Functions - AWS Developer Associate Guide
What Are Stage Variables in API Gateway with Lambda Functions?
Stage variables are name-value pairs that act as configuration variables associated with a deployment stage in Amazon API Gateway. They allow you to manage different configurations for your Lambda functions across multiple environments (development, staging, production) without changing your API configuration.
Why Are Stage Variables Important?
Stage variables are crucial for several reasons:
• Environment Management: They enable you to point to different Lambda function versions or aliases based on the deployment stage • Configuration Flexibility: You can change backend endpoints, Lambda functions, or other settings per stage • Cost Efficiency: Use the same API Gateway configuration across multiple environments • Safe Deployments: Test changes in lower environments before promoting to production • Reduced Code Duplication: Maintain a single API definition that works across all stages
How Stage Variables Work with Lambda Functions
Stage variables work through a reference system in API Gateway:
1. Define Stage Variables: In API Gateway, you create stage variables for each deployment stage (dev, test, prod)
2. Reference in Integration: Use the syntax ${stageVariables.variableName} in your Lambda function ARN
3. Lambda Function ARN Format: arn:aws:lambda:region:account-id:function:${stageVariables.lambdaAlias} 4. Runtime Resolution: When a request comes in, API Gateway substitutes the stage variable with its actual value for that stage
Common Use Cases
• Lambda Aliases: Point to different Lambda aliases (dev, prod) using stage variables • Lambda Versions: Reference specific Lambda versions per environment • HTTP Endpoints: Configure different backend URLs for each stage • Parameter Mapping: Pass stage-specific values to your Lambda functions
Setting Up Stage Variables
1. Create your Lambda function with multiple versions or aliases 2. In API Gateway, deploy your API to a stage 3. Navigate to the stage settings and add stage variables 4. Update your Lambda integration to use ${stageVariables.yourVariable}5. Grant API Gateway permission to invoke each Lambda version or alias
Important Permission Requirement
You must add a resource-based policy to your Lambda function allowing API Gateway to invoke it. This permission must be added for each Lambda alias or version that stage variables might reference.
Exam Tips: Answering Questions on Stage Variables in Lambda Functions
• Remember the Syntax: Stage variables are referenced using ${stageVariables.variableName} - this syntax appears frequently in exam questions
• Permissions Are Key: If a question mentions errors invoking Lambda through stage variables, think about resource-based policies on the Lambda function
• Stage Variables vs Environment Variables: Do not confuse API Gateway stage variables with Lambda environment variables - they serve different purposes
• Alias Integration: Stage variables commonly work with Lambda aliases to implement blue-green deployments or canary releases
• Scope Understanding: Stage variables are scoped to a specific stage - each stage can have different values for the same variable name
• Use Case Recognition: When questions describe scenarios requiring different Lambda functions per environment with the same API, stage variables are typically the answer
• Cannot Store Secrets: Stage variables are not encrypted and should not store sensitive information - use AWS Secrets Manager or Parameter Store instead
• Mapping Templates: Stage variables can be used in mapping templates to transform requests and responses dynamically
Key Points for the Exam
• Stage variables enable configuration management across deployment stages • They are defined at the stage level in API Gateway • Lambda permissions must explicitly allow invocation from API Gateway for each referenced version or alias • Stage variables support blue-green and canary deployment patterns when combined with Lambda aliases • They reduce the need for multiple API Gateway deployments for different environments