API Gateway stage variables are name-value pairs that act as configuration variables associated with a deployment stage in Amazon API Gateway. They function similarly to environment variables and allow you to manage stage-specific configuration without modifying your API setup.
Stage variables ena…API Gateway stage variables are name-value pairs that act as configuration variables associated with a deployment stage in Amazon API Gateway. They function similarly to environment variables and allow you to manage stage-specific configuration without modifying your API setup.
Stage variables enable you to configure different backends, Lambda function aliases, or HTTP endpoints for each stage (such as dev, test, and prod) of your API. This makes it possible to use a single API configuration while dynamically routing requests to different resources based on the current stage.
Common use cases for stage variables include:
1. **Lambda Function Aliases**: You can reference different Lambda function versions or aliases by using stage variables. For example, ${stageVariables.lambdaAlias} can point to 'dev' in development and 'prod' in production.
2. **Backend Endpoints**: Stage variables can store different HTTP endpoint URLs, allowing your API to connect to staging or production backend services accordingly.
3. **Configuration Values**: Store database connection strings, feature flags, or other configuration parameters that vary between environments.
To use stage variables, you define them in the stage settings of your API Gateway deployment. They can then be referenced in integration request URLs, Lambda function ARNs, request and response mapping templates, and parameter mappings using the syntax ${stageVariables.variableName}.
When working with Lambda integrations, you must grant API Gateway permission to invoke the Lambda function for each stage variable value. This requires adding resource-based policies to your Lambda functions.
Stage variables support alphanumeric characters, hyphens, underscores, and periods. They are passed to your backend as part of the context object, making them accessible in Lambda functions through the event.stageVariables property.
For the AWS Developer Associate exam, understanding how stage variables facilitate multi-environment deployments and enable dynamic API configuration is essential for designing scalable serverless applications.
API Gateway Stage Variables - Complete Guide
What Are API Gateway Stage Variables?
Stage variables are name-value pairs that act as configuration variables associated with a deployment stage in Amazon API Gateway. They function similarly to environment variables and allow you to manage stage-specific configuration without modifying your API definition.
Why Are Stage Variables Important?
Stage variables are crucial because they enable you to:
• Decouple configuration from code - Change backend endpoints, Lambda function ARNs, or other settings per stage • Manage multiple environments - Use the same API definition across dev, test, and prod stages • Reduce deployment complexity - Avoid creating separate APIs for each environment • Enable A/B testing - Route traffic to different Lambda versions or backend services • Simplify Lambda alias management - Point to different Lambda aliases per stage
How Stage Variables Work
Stage variables are defined at the stage level and can be referenced in your API configuration using the syntax: ${stageVariables.variableName}
Common Use Cases:
1. Lambda Function ARN: arn:aws:lambda:region:account:function:${stageVariables.lambdaAlias}2. HTTP Endpoint URL: https://${stageVariables.backendHost}/api/v1 3. Parameter Mapping: Pass stage-specific values to integrations
Configuration Locations:
Stage variables can be used in: • Lambda function ARNs • HTTP/HTTPS endpoint URLs • Parameter mapping templates • Mapping templates for request/response transformations
Setting Up Stage Variables
1. Navigate to API Gateway in the AWS Console 2. Select your API and go to Stages 3. Choose the specific stage (dev, prod, etc.) 4. Click on the Stage Variables tab 5. Add key-value pairs for your configuration
Lambda Permission Requirements
When using stage variables with Lambda functions, you must grant API Gateway permission to invoke each Lambda function or alias that might be referenced. This requires adding a resource-based policy to your Lambda function.
Exam Tips: Answering Questions on API Gateway Stage Variables
Key Points to Remember:
• Stage variables are stage-specific, not API-wide • The reference syntax is ${stageVariables.variableName} • They enable environment-specific configurations within a single API • Stage variables can reference Lambda aliases for version management • You need Lambda resource-based policies for each function/alias referenced
Common Exam Scenarios:
1. Multi-environment deployment: When asked how to deploy the same API to multiple environments with different backends, stage variables are the answer
2. Lambda versioning integration: Questions about pointing API Gateway to different Lambda versions per stage typically involve stage variables combined with Lambda aliases
3. Dynamic endpoint configuration: If a scenario describes needing different HTTP endpoints per deployment stage, think stage variables
4. Configuration management: Questions about managing environment-specific settings in API Gateway point to stage variables
Watch Out For:
• Do not confuse stage variables with Lambda environment variables - they serve different purposes • Stage variables are different from API Gateway usage plans • Remember that stage variables require proper IAM permissions when invoking Lambda functions • Stage variables are not encrypted - do not store sensitive data like passwords in them