Lambda function concept in AWS - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ service_behavior

intermediate

What happens when a Lambda function exceeds its configured timeout?

You have set a Lambda function timeout to 10 seconds. The function runs longer than 10 seconds. What is the result?

A The function restarts automatically and runs again from the start.

B The function continues running until it finishes, ignoring the timeout.

C The function pauses and resumes after the timeout period.

D The function is forcibly stopped and an error is returned.

💡 Hint

Think about how time limits protect resources in cloud functions.

When a Lambda function runs longer than its configured timeout, AWS forcibly stops it and returns a timeout error. This prevents runaway costs and resource use.

❓ Architecture

intermediate

Which AWS service is best to trigger a Lambda function on a schedule?

You want to run a Lambda function every day at 8 AM automatically. Which AWS service should you use to trigger it?

A Amazon S3

B Amazon EventBridge (CloudWatch Events)

C AWS IAM

D Amazon DynamoDB

💡 Hint

Think about services that can schedule tasks or events.

Amazon EventBridge (formerly CloudWatch Events) can create rules to trigger Lambda functions on schedules like cron expressions.

❓ security

advanced

What is the best practice for Lambda function permissions to access an S3 bucket?

You want your Lambda function to read files from a specific S3 bucket. Which approach follows the best security practice?

A Attach an IAM role to the Lambda function with permissions limited to read only the specific S3 bucket.

B Embed AWS access keys with full S3 access inside the Lambda function code.

C Grant public read access to the S3 bucket so Lambda can access it without permissions.

D Use the Lambda function's default execution role without modifying permissions.

💡 Hint

Consider the principle of least privilege and secure credential management.

Assigning a specific IAM role with limited permissions to the Lambda function is secure and follows best practices. Embedding keys or making buckets public is insecure.

❓ Configuration

advanced

What is the effect of increasing the memory allocation of a Lambda function?

You increase the memory setting of a Lambda function from 128 MB to 1024 MB. What changes occur?

A The CPU power allocated to the function increases proportionally, potentially reducing execution time.

B Only the memory increases; CPU power and execution time remain the same.

C The function's timeout automatically increases to allow longer execution.

D The function's network bandwidth decreases to balance resource usage.

💡 Hint

Think about how AWS bundles CPU with memory for Lambda functions.

In AWS Lambda, CPU power scales with memory allocation. Increasing memory also increases CPU, which can speed up execution.

✅ Best Practice

expert

How should you handle environment variables in Lambda for sensitive data?

You need to store database passwords for your Lambda function securely. What is the best practice?

A Hardcode the passwords inside the Lambda function code for faster access.

B Store the passwords as plain text environment variables in the Lambda configuration.

C Use AWS Secrets Manager or AWS Systems Manager Parameter Store with encryption, and reference them in the Lambda function.

D Send the passwords as part of the Lambda event payload each time it runs.

💡 Hint

Consider secure storage and retrieval of secrets in AWS.

Using AWS Secrets Manager or Parameter Store with encryption is the best practice to keep sensitive data secure and separate from code.

Practice

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

easy

A. To store large amounts of data

B. To run code automatically without managing servers

C. To create virtual machines

D. To manage user permissions

Solution

1. Step 1: Understand Lambda's role

   AWS Lambda runs your code without needing you to manage servers.

2. Step 2: Compare options

   Options A, C, and D describe other AWS services, not Lambda.

3. Final Answer:

   To run code automatically without managing servers -> Option B

4. Quick Check:

   Lambda = serverless code execution [OK]

Hint: Lambda runs code without servers, not storage or VMs [OK]

Common Mistakes:

• Confusing Lambda with storage services
• Thinking Lambda creates virtual machines
• Assuming Lambda manages user permissions

2. Which of the following is the correct way to define a simple AWS Lambda function handler in Python?

easy

A. lambda handler(event): print('Hello World')

B. function handler(event) { return 'Hello World'; }

C. def handler(event, context): return 'Hello World'

D. def handler(): print('Hello World')

Solution

1. Step 1: Identify correct Python Lambda handler syntax

   Lambda handlers in Python must accept two parameters: event and context.

2. Step 2: Check each option

   def handler(event, context): return 'Hello World' correctly defines a Python function with event and context parameters and returns a string. function handler(event) { return 'Hello World'; } is JavaScript syntax. lambda handler(event): print('Hello World') misuses lambda keyword. def handler(): print('Hello World') lacks required parameters.

3. Final Answer:

   def handler(event, context): return 'Hello World' -> Option C

4. Quick Check:

   Python Lambda handler needs event and context [OK]

Hint: Python Lambda handlers always have (event, context) parameters [OK]

Common Mistakes:

• Using JavaScript syntax in Python Lambda
• Omitting event or context parameters
• Misusing lambda keyword for handler

3. Given this AWS Lambda Python code:

def handler(event, context):
    name = event.get('name', 'Guest')
    return f"Hello, {name}!"

What will be the output if the event is {}?

medium

A. "Hello, Guest!"

B. "Hello, None!"

C. Error: 'name' key missing

D. "Hello, !"

Solution

1. Step 1: Analyze event input and code behavior

   The event is an empty dictionary, so event.get('name', 'Guest') returns the default 'Guest'.

2. Step 2: Determine return value

   The function returns the string "Hello, Guest!" because 'name' is not in event.

3. Final Answer:

   "Hello, Guest!" -> Option A

4. Quick Check:

   Missing key uses default value 'Guest' [OK]

Hint: event.get with default returns default if key missing [OK]

Common Mistakes:

• Assuming missing key causes error
• Thinking None is returned instead of default
• Ignoring default value in get()

4. You wrote this AWS Lambda function in Python:

def handler(event, context):
    return event['message']

When triggered with event {}, it throws a KeyError. How can you fix it?

medium

A. Use event.get('message', 'No message') instead of event['message']

B. Remove the return statement

C. Add a print statement before return

D. Change function name to lambda_handler

Solution

1. Step 1: Identify cause of KeyError

   Accessing event['message'] when 'message' key is missing causes KeyError.

2. Step 2: Use safe access method

   Replacing event['message'] with event.get('message', 'No message') avoids error by providing default.

3. Final Answer:

   Use event.get('message', 'No message') instead of event['message'] -> Option A

4. Quick Check:

   Use get() to avoid KeyError on missing keys [OK]

Hint: Use get() with default to prevent KeyError [OK]

Common Mistakes:

• Ignoring missing key causes error
• Thinking print fixes KeyError
• Assuming function name affects key access

5. You want an AWS Lambda function to process image uploads to S3 and resize them. Which combination of AWS services and Lambda features is best suited for this task?

hard

A. Use Lambda to create EC2 instances that resize images

B. Run Lambda on a schedule to scan S3 and resize images manually

C. Upload images directly to Lambda storage for resizing

D. Use S3 event trigger on object creation to invoke Lambda, which resizes images and saves back to S3

Solution

1. Step 1: Understand event-driven processing

   S3 can trigger Lambda automatically when new objects are created, ideal for immediate processing.

2. Step 2: Evaluate options for image resizing

   Use S3 event trigger on object creation to invoke Lambda, which resizes images and saves back to S3 uses S3 event triggers and Lambda to resize and save images back to S3, which is efficient and serverless. Run Lambda on a schedule to scan S3 and resize images manually delays processing and requires scanning. Use Lambda to create EC2 instances that resize images misuses Lambda to create servers. Upload images directly to Lambda storage for resizing is invalid as Lambda has no persistent storage for uploads.

3. Final Answer:

   Use S3 event trigger on object creation to invoke Lambda, which resizes images and saves back to S3 -> Option D

4. Quick Check:

   S3 event triggers + Lambda = best for image processing [OK]

Hint: Use S3 event triggers to run Lambda on uploads [OK]

Common Mistakes:

• Thinking Lambda can store files persistently
• Using scheduled scans instead of event triggers
• Misusing Lambda to create servers