Lambda execution model in AWS - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to specify the runtime environment for an AWS Lambda function.

AWS

Runtime = "[1]"

Drag options to blanks, or click blank then click option'

Anodejs14.x

Bpython3.9

Cjava8

Dgo1.x

Attempts:

3 left

💡 Hint

Common Mistakes

Choosing an unsupported or deprecated runtime version.

Using a runtime that does not match the function code language.

The runtime environment defines the language and version your Lambda function uses. Here, nodejs14.x is a valid and common runtime.

2fill in blank

medium

Complete the code to set the memory size for an AWS Lambda function.

AWS

MemorySize = [1]

Drag options to blanks, or click blank then click option'

A512

B4096

C2048

D128

Attempts:

3 left

💡 Hint

Common Mistakes

Using memory sizes not supported by Lambda (e.g., too low or too high).

Putting memory size as a string instead of a number.

MemorySize is set in megabytes. 512 MB is a common balanced choice for Lambda functions.

3fill in blank

hard

Fix the error in the handler configuration for an AWS Lambda function.

AWS

Handler = "[1]"

Drag options to blanks, or click blank then click option'

Ahandler.index

Bindex.handler

Cmain.handler

Dapp.lambda

Attempts:

3 left

💡 Hint

Common Mistakes

Swapping the order of file and function names.

Using incorrect file or function names.

The handler is specified as fileName.functionName. Here, index.handler means the handler function inside the index file.

4fill in blank

hard

Fill both blanks to configure the timeout and environment variables for an AWS Lambda function.

AWS

Timeout = [1]
Environment = {"Variables": {"STAGE": "[2]"}}

Drag options to blanks, or click blank then click option'

A30

B60

Cdev

Dprod

Attempts:

3 left

💡 Hint

Common Mistakes

Setting timeout too high or too low.

Using incorrect environment variable names or values.

Timeout is set in seconds; 30 seconds is a common timeout. Environment variables are key-value pairs; here, STAGE is set to dev to indicate the development environment.

5fill in blank

hard

Fill all three blanks to define the AWS Lambda function's role, runtime, and handler.

AWS

Role = "[1]"
Runtime = "[2]"
Handler = "[3]"

Drag options to blanks, or click blank then click option'

Aarn:aws:iam::123456789012:role/lambda-exec-role

Bpython3.9

Clambda_function.lambda_handler

Dnodejs16.x

Attempts:

3 left

💡 Hint

Common Mistakes

Using incorrect or incomplete IAM role ARN.

Mismatching runtime and handler names.

The Role is the IAM role ARN that grants permissions. The Runtime specifies the language version, here Python 3.9. The Handler points to the function inside the code file.

Practice

1. What happens when an AWS Lambda function is not triggered by any event?

easy

A. The function does not run and no charges occur.

B. The function runs continuously in the background.

C. The function runs once every hour automatically.

D. The function runs only when manually started from the console.

Solution

1. Step 1: Understand Lambda's event-driven model

   A Lambda function runs only when triggered by an event, such as an API call or file upload.

2. Step 2: Consider billing and execution behavior

   If no event triggers the function, it does not execute and you are not charged.

3. Final Answer:

   The function does not run and no charges occur. -> Option A

4. Quick Check:

   Lambda runs only on events = C [OK]

Hint: Lambda runs only on events, no event means no run [OK]

Common Mistakes:

• Thinking Lambda runs continuously without events
• Assuming Lambda runs on a schedule by default
• Believing manual start is required for all executions

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

easy

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

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

C. handler(event, context) => { return 'Hello World'; }

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

Solution

1. Step 1: Recall Python Lambda handler signature

   In Python, the handler must accept two parameters: event and context.

2. Step 2: Check syntax correctness

   def handler(event, context): return 'Hello World' correctly defines a Python function with event and context and returns a string.

3. Final Answer:

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

4. Quick Check:

   Python handler(event, context) = A [OK]

Hint: Python Lambda handlers need event and context parameters [OK]

Common Mistakes:

• Using JavaScript syntax in Python handler
• Omitting context parameter
• Defining handler without parameters

3. Given this Python Lambda handler code:

def handler(event, context):
    return event['value'] * 2

What is the output if the event is {"value": 5}?

medium

A. Error: 'value' key missing

B. 5

C. 10

D. None

Solution

1. Step 1: Understand the handler logic

   The handler multiplies the 'value' from event by 2.

2. Step 2: Calculate output for event {'value': 5}

   5 * 2 = 10, so the function returns 10.

3. Final Answer:

   10 -> Option C

4. Quick Check:

   5 times 2 equals 10 [OK]

Hint: Multiply event['value'] by 2 for output [OK]

Common Mistakes:

• Confusing event keys or missing them
• Assuming function returns input unchanged
• Expecting error when key exists

4. This Lambda function code causes an error when triggered:

def handler(event, context):
    return event['data'] * 3

What is the likely cause?

medium

A. The function is missing the context parameter.

B. The event dictionary does not have the 'data' key.

C. The return statement syntax is incorrect.

D. Lambda functions cannot multiply values.

Solution

1. Step 1: Identify cause of error in code

   The function tries to access event['data'], which may not exist.

2. Step 2: Understand error from missing key

   If 'data' key is missing in event, a KeyError occurs causing the function to fail.

3. Final Answer:

   The event dictionary does not have the 'data' key. -> Option B

4. Quick Check:

   Missing event key causes error = B [OK]

Hint: Check if event keys exist before using them [OK]

Common Mistakes:

• Assuming context parameter missing causes error
• Thinking return syntax is wrong
• Believing Lambda cannot do arithmetic

5. You want your Lambda function to process multiple events concurrently without waiting for previous executions. Which Lambda feature supports this behavior?

hard

A. Automatic scaling with multiple concurrent executions

B. Manual start of multiple Lambda instances

C. Scheduled triggers to queue events

D. Using a single-threaded execution model

Solution

1. Step 1: Understand Lambda concurrency

   Lambda automatically scales by running multiple instances to handle events concurrently.

2. Step 2: Eliminate incorrect options

   Manual start and single-threaded models do not support concurrency; scheduled triggers queue events but don't scale automatically.

3. Final Answer:

   Automatic scaling with multiple concurrent executions -> Option A

4. Quick Check:

   Lambda auto-scales for concurrency = D [OK]

Hint: Lambda auto-scales to run many events at once [OK]

Common Mistakes:

• Thinking manual start is needed for concurrency
• Confusing scheduling with scaling
• Assuming Lambda runs single-threaded only