AWS Lambda environment variables are key-value pairs that allow you to dynamically configure your Lambda function's behavior at runtime, separate from your code. They provide a flexible way to store configuration settings, database connection strings, API keys, and other parameters that might chang…AWS Lambda environment variables are key-value pairs that allow you to dynamically configure your Lambda function's behavior at runtime, separate from your code. They provide a flexible way to store configuration settings, database connection strings, API keys, and other parameters that might change between environments like development, staging, and production.
When you create or update a Lambda function, you can define environment variables through the AWS Console, AWS CLI, CloudFormation, or AWS SAM. These variables are accessible within your function code through standard environment variable methods specific to your runtime. For example, in Python you use os.environ['VARIABLE_NAME'], while in Node.js you access them via process.env.VARIABLE_NAME.
Lambda environment variables support encryption at rest using AWS Key Management Service (KMS). By default, Lambda encrypts environment variables using a service-managed key. However, for enhanced security, you can configure customer-managed KMS keys to encrypt sensitive data. Lambda also provides encryption helpers that allow you to encrypt environment variable values before deployment and decrypt them during function execution.
There are some limitations to consider. The total size of all environment variables cannot exceed 4 KB. Variable names must start with a letter and can only contain letters, numbers, and underscores. Additionally, certain reserved variable names are used by the Lambda runtime and should not be overwritten.
Best practices include using environment variables for configuration that varies between deployment stages, storing sensitive information with encryption enabled, and avoiding hardcoding values in your function code. This approach promotes code reusability and makes it easier to manage different configurations across multiple environments.
Environment variables integrate well with AWS Systems Manager Parameter Store and AWS Secrets Manager, allowing you to reference stored parameters and secrets dynamically, providing an additional layer of security and centralized configuration management for your serverless applications.
Lambda Environment Variables
What Are Lambda Environment Variables?
Lambda environment variables are key-value pairs that you can define and access within your Lambda function code. They allow you to configure your function's behavior without modifying the code itself, making your functions more portable and easier to manage across different environments (development, staging, production).
Why Are Environment Variables Important?
Environment variables are crucial for several reasons:
• Security: Store sensitive information like database credentials, API keys, and connection strings outside your code • Flexibility: Change function behavior across environments by simply updating variable values • Best Practices: Follow the twelve-factor app methodology by separating configuration from code • Maintainability: Update configuration values in the AWS Console or CLI rather than redeploying code
How Environment Variables Work in Lambda
When you create or update a Lambda function, you can define environment variables in the function configuration. These variables are:
• Available to your function code through standard environment variable access methods • Encrypted at rest using AWS KMS (Key Management Service) • Can use the default Lambda service key or a customer-managed CMK • Limited to a total size of 4 KB for all environment variables combined
• Encryption in transit: Variables are encrypted when deployed using the Lambda service key • Encryption at rest: By default, variables are encrypted at rest with the AWS managed key • Encryption helpers: You can encrypt sensitive values before deployment using your own KMS key, then decrypt them at runtime in your function code
Reserved Environment Variables
AWS Lambda sets several reserved environment variables that you cannot override:
• AWS_REGION - The AWS Region where the function runs • AWS_LAMBDA_FUNCTION_NAME - The name of the function • AWS_LAMBDA_FUNCTION_VERSION - The version of the function • AWS_LAMBDA_FUNCTION_MEMORY_SIZE - Memory allocated to the function • AWS_ACCESS_KEY_ID, AWS_SECRET_ACCESS_KEY, AWS_SESSION_TOKEN - Credentials from the execution role
Exam Tips: Answering Questions on Lambda Environment Variables
• Remember the 4 KB limit: All environment variables combined cannot exceed 4 KB in size • KMS encryption: For sensitive data, use KMS to encrypt values before storing them, then decrypt at runtime using the KMS Decrypt API • Encryption at rest vs. in transit: Understand that Lambda encrypts environment variables at rest by default, but for additional security with sensitive values, use encryption helpers • Customer-managed keys: When questions mention compliance or additional control over encryption keys, think about using a customer-managed CMK instead of the default service key • No code changes needed: When a scenario asks how to change configuration across environments, environment variables are the answer - not code modifications • Versioning consideration: Environment variables are included in Lambda versions - changing variables creates a need for a new version • Access patterns: Know the standard methods to access environment variables in Python (os.environ), Node.js (process.env), and Java (System.getenv) • Security scenarios: If a question asks about storing database passwords or API keys securely in Lambda, the answer involves environment variables encrypted with KMS, or alternatively AWS Secrets Manager or Systems Manager Parameter Store for more complex scenarios