Environment variables in Lambda in AWS - Cheat Sheet & Quick Revision

Recall & Review

beginner

What are environment variables in AWS Lambda?

Environment variables in AWS Lambda are key-value pairs that you can set to store configuration settings. They help your function access settings without hardcoding them in the code.

beginner

How do environment variables improve Lambda function management?

They let you change settings like database URLs or API keys without changing the code. This makes your function easier to update and more secure.

intermediate

Can environment variables in Lambda be encrypted? If yes, how?

Yes, Lambda supports encrypting environment variables using AWS Key Management Service (KMS). This keeps sensitive data like passwords safe.

beginner

How can you access environment variables inside a Lambda function?

Inside your Lambda code, you can read environment variables using standard methods. For example, in Node.js, use process.env.VARIABLE_NAME.

intermediate

What is a best practice when using environment variables in Lambda?

Avoid putting sensitive data directly in environment variables unless encrypted. Use AWS KMS encryption and restrict access with IAM roles.

What is the main purpose of environment variables in AWS Lambda?

A Increase the memory of the Lambda function

B Store configuration settings separately from code

C Control the number of Lambda executions

D Manage user permissions

Environment variables store configuration settings separately from code, making it easier to manage and update.

How can you secure sensitive environment variables in Lambda?

A Encrypt them using AWS KMS

B Store them in plain text

C Hardcode them in the Lambda function

D Disable environment variables

AWS KMS encryption protects sensitive environment variables from unauthorized access.

Which of the following is a correct way to access an environment variable named 'API_KEY' in Node.js Lambda code?

A lambda.env.API_KEY

B env.API_KEY

C process.env.API_KEY

D getEnv('API_KEY')

In Node.js, environment variables are accessed using process.env.VARIABLE_NAME.

What happens if you update an environment variable in Lambda?

A The new value is used in the next function invocation

B The function crashes immediately

C The old value remains forever

D The Lambda function restarts automatically

Updated environment variables take effect on the next invocation of the Lambda function.

Which AWS service is used to encrypt Lambda environment variables?

A Amazon EC2

B Amazon S3

C AWS CloudTrail

D AWS Key Management Service (KMS)

AWS KMS is the service used to encrypt and manage keys for Lambda environment variables.

Explain what environment variables are in AWS Lambda and why they are useful.

Think about how you might keep your app settings outside the code.

Describe how to securely manage sensitive data using environment variables in Lambda.

Focus on encryption and access control.

Practice

1. What is the main purpose of environment variables in an AWS Lambda function?

easy

A. To store configuration settings outside the code for flexibility

B. To write logs directly to CloudWatch

C. To increase the memory allocated to the Lambda function

D. To define the runtime language of the Lambda function

Solution

1. Step 1: Understand environment variables role

   Environment variables hold configuration data separate from code, making functions flexible.

2. Step 2: Compare with other options

   Logging, memory, and runtime are unrelated to environment variables.

3. Final Answer:

   To store configuration settings outside the code for flexibility -> Option A

4. Quick Check:

   Environment variables = configuration outside code [OK]

Hint: Environment variables hold config, not code or logs [OK]

Common Mistakes:

• Confusing environment variables with logging settings
• Thinking environment variables control memory or runtime
• Assuming environment variables store code

2. Which of the following is the correct way to define an environment variable named API_KEY with value 12345 in AWS Lambda console?

easy

A. Create a CloudWatch alarm named API_KEY with threshold 12345

B. Add a tag with key API_KEY and value 12345

C. Write export API_KEY=12345 in the Lambda function code

D. Set key as API_KEY and value as 12345 in the Environment Variables section

Solution

1. Step 1: Identify environment variable setup

   Environment variables are set as key-value pairs in the Lambda console's Environment Variables section.

2. Step 2: Eliminate incorrect options

   Tags, code exports, and CloudWatch alarms do not define environment variables.

3. Final Answer:

   Set key as API_KEY and value as 12345 in the Environment Variables section -> Option D

4. Quick Check:

   Environment variables = key-value pairs in Lambda console [OK]

Hint: Set env vars in Lambda console's Environment Variables section [OK]

Common Mistakes:

• Confusing tags with environment variables
• Trying to set env vars inside code with export
• Using unrelated AWS features like CloudWatch alarms

3. Given this Python Lambda function code:

import os
def lambda_handler(event, context):
    return os.environ.get('MODE', 'default')

If the environment variable MODE is set to production, what will the function return?

medium

A. "default"

B. None

C. "production"

D. An error occurs

Solution

1. Step 1: Understand os.environ.get usage

   os.environ.get('MODE', 'default') returns the value of MODE if set, else 'default'.

2. Step 2: Apply given environment variable

   Since MODE is set to 'production', the function returns 'production'.

3. Final Answer:

   "production" -> Option C

4. Quick Check:

   Env var MODE='production' returns 'production' [OK]

Hint: os.environ.get returns env var value or default if missing [OK]

Common Mistakes:

• Assuming default is always returned
• Expecting None if variable exists
• Thinking code throws error if env var exists

4. A developer sets an environment variable DB_PASSWORD in Lambda console but the function code returns None when accessing it. What is the most likely cause?

medium

A. Lambda function memory is too low

B. The environment variable key is misspelled in the code

C. The environment variable value is encrypted and inaccessible

D. The Lambda function timeout is too short

Solution

1. Step 1: Check environment variable access

   If code returns None, likely the key used in code does not match the set key.

2. Step 2: Exclude unrelated causes

   Memory size, encryption, or timeout do not cause None return for env var access.

3. Final Answer:

   The environment variable key is misspelled in the code -> Option B

4. Quick Check:

   Misspelled env var key returns None [OK]

Hint: Check spelling of env var keys in code vs console [OK]

Common Mistakes:

• Blaming memory or timeout for env var issues
• Assuming encryption blocks access without decryption
• Not verifying exact key names

5. You want to securely store a database password in a Lambda environment variable but avoid exposing it in plain text. Which approach is best practice?

hard

A. Use AWS Lambda environment variables with encryption enabled and grant decryption permissions

B. Hardcode the password directly in the Lambda function code

C. Store the password in a public S3 bucket and read it at runtime

D. Send the password as a query parameter in API requests

Solution

1. Step 1: Understand secure storage options

   Lambda environment variables support encryption with AWS KMS and access control.

2. Step 2: Evaluate other options

   Hardcoding, public S3, or sending passwords in query parameters expose secrets and are insecure.

3. Final Answer:

   Use AWS Lambda environment variables with encryption enabled and grant decryption permissions -> Option A

4. Quick Check:

   Encrypted env vars + permissions = secure secret storage [OK]

Hint: Encrypt env vars and control access for secrets [OK]

Common Mistakes:

• Hardcoding secrets in code
• Using public storage for passwords
• Exposing secrets in API requests