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Exam AWS Certified Developer - Associate DVA-C02 topic 1 question 222 discussion

Exam question from Amazon's AWS Certified Developer - Associate DVA-C02
Question #: 222
Topic #: 1
[All AWS Certified Developer - Associate DVA-C02 Questions]

A developer is designing a serverless application that customers use to select seats for a concert venue. Customers send the ticket requests to an Amazon API Gateway API with an AWS Lambda function that acknowledges the order and generates an order ID. The application includes two additional Lambda functions: one for inventory management and one for payment processing. These two Lambda functions run in parallel and write the order to an Amazon Dynamo DB table.

The application must provide seats to customers according to the following requirements. If a seat is accidently sold more than once, the first order that the application received must get the seat. In these cases, the application must process the payment for only the first order. However, if the first order is rejected during payment processing, the second order must get the seat. In these cases, the application must process the payment for the second order.

Which solution will meet these requirements?

  • A. Send the order ID to an Amazon Simple Notification Service (Amazon SNS) FIFO topic that fans out to one Amazon Simple Queue Service (Amazon SQS) FIFO queue for inventory management and another SQS FIFO queue for payment processing.
  • B. Change the Lambda function that generates the order ID to initiate the Lambda function for inventory management. Then initiate the Lambda function for payment processing.
  • C. Send the order ID to an Amazon Simple Notification Service (Amazon SNS) topic. Subscribe the Lambda functions for inventory management and payment processing to the topic.
  • D. Deliver the order ID to an Amazon Simple Queue Service (Amazon SQS) queue. Configure the Lambda functions for inventory management and payment processing to poll the queue.
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Suggested Answer: A 🗳️
by Claire_KMT at Oct. 28, 2023, 12:36 p.m.
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MarkTpTTT55
Highly Voted 1 year, 6 months ago
Selected Answer: A
A. The only viable solution
upvoted 10 times
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SerialiDr
Highly Voted 1 year, 3 months ago
Selected Answer: A
Here's why this solution is most appropriate: SNS FIFO Topic: A First-In-First-Out (FIFO) SNS topic ensures that messages are delivered in the exact order they are sent. This is critical for maintaining the order of ticket requests. SQS FIFO Queues: By having two separate FIFO queues for inventory management and payment processing, the application can process these aspects in parallel while still maintaining the order integrity. The FIFO nature of the queues ensures that if a seat is sold more than once, the first order received is processed first. Order Processing Logic: With this setup, if the first order is rejected during payment processing, the second order can be processed next. The sequential processing inherent in FIFO queues ensures that this logic can be correctly implemented.
upvoted 5 times
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BrainFried
Most Recent 9 months, 1 week ago
None of these answers are correct. People say it is A - well then what prevents payment processing for order #1 if the inventory lambda failed to allocate a seat for order #1? The correct answer should be for the order processing lambda to place orders into a queue (e.g. FIFO SQS) and then seat allocation lambda should poll this queue, check if seating is available and if so it should then invoke the payment processing lambda. This option isn't available. The next best option would be Option B. Better than A, since you won't be charged for an order where seating isn't available. If I am wrong, please explain it. Would love to hear. Thanks
upvoted 2 times
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65703c1
11 months, 2 weeks ago
Selected Answer: A
A is the correct answer.
upvoted 1 times
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nder
1 year, 1 month ago
Selected Answer: A
FIFO is the only option that maintains ordering.
upvoted 2 times
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Claire_KMT
1 year, 6 months ago
Selected Answer: D
D. Deliver the order ID to an Amazon Simple Queue Service (Amazon SQS) queue. Configure the Lambda functions for inventory management and payment processing to poll the queue.
upvoted 2 times
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Claire_KMT
1 year, 6 months ago
D. Deliver the order ID to an Amazon Simple Queue Service (Amazon SQS) queue. Configure the Lambda functions for inventory management and payment processing to poll the queue.
upvoted 1 times
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