[Solved] You want your AWS Lambda handler to process an event with optional user key. If user is missing, return status 400 with message 'User missing'.... Which handler code correctly implements this? | AWS

AWS - Lambda

You want your AWS Lambda handler to process an event with optional user key. If user is missing, return status 400 with message 'User missing'. Otherwise, return status 200 with 'Hello, <user>'. Which handler code correctly implements this?

Adef handler(event): if 'user' in event: return {'statusCode': 400, 'body': 'User missing'} return {'statusCode': 200, 'body': f"Hello, {event['user']}"}

Bdef handler(event, context): return {'statusCode': 200, 'body': f"Hello, {event['user']}"}

Cdef handler(event, context): if event['user'] == None: return {'statusCode': 400, 'body': 'User missing'} return {'statusCode': 200, 'body': 'Hello, user'}

Ddef handler(event, context): if 'user' not in event: return {'statusCode': 400, 'body': 'User missing'} return {'statusCode': 200, 'body': f"Hello, {event['user']}"}

Step-by-Step Solution

Solution:

Step 1: Check parameter correctness
Lambda handler must have event and context parameters.
Step 2: Validate logic for user key
def handler(event, context): if 'user' not in event: return {'statusCode': 400, 'body': 'User missing'} return {'statusCode': 200, 'body': f"Hello, {event['user']}"} correctly checks if 'user' key is missing and returns 400 with message. Then returns 200 with personalized greeting. def handler(event, context): return {'statusCode': 200, 'body': f"Hello, {event['user']}"} does not check for missing user. def handler(event, context): if event['user'] == None: return {'statusCode': 400, 'body': 'User missing'} return {'statusCode': 200, 'body': 'Hello, user'} incorrectly checks if event['user'] == None which causes error if key missing. def handler(event): if 'user' in event: return {'statusCode': 400, 'body': 'User missing'} return {'statusCode': 200, 'body': f"Hello, {event['user']}"} reverses logic and misses context.
Final Answer:
def handler(event, context): if 'user' not in event: return {'statusCode': 400, 'body': 'User missing'} return {'statusCode': 200, 'body': f"Hello, {event['user']}" } -> Option D
Quick Check:
Check key presence before access to avoid errors [OK]

Quick Trick: Check key exists before access; include event and context [OK]

Common Mistakes:

MISTAKES

Missing context parameter
Accessing missing keys without check
Returning wrong status codes

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Which handler code correctly implements this?

Step 1: Check parameter correctness

Step 2: Validate logic for user key

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