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Difficulty: EasyServerless and Automated Scaling Architectures for Cost Efficiency

A company is developing a new event-driven registration system that experiences highly unpredictable, short spikes in traffic during marketing campaigns, with long periods of complete inactivity. The system needs to execute lightweight backend logic to process registration requests, maintain strict processing sequence for order transactions, and store the registration details. The company wants to minimize costs during idle periods. Which two AWS service configurations should a solutions architect recommend to meet these requirements? (Select TWO.)

  1. AWS Lambda to execute the short-lived backend logic.Answer
  2. Amazon DynamoDB in on-demand capacity mode to store registration details.Answer
  3. C
    An AWS Lambda function configured with a continuous loop to poll for incoming orders 24/7.
  4. D
    Amazon DynamoDB with provisioned capacity mode set to the maximum expected peak load.
  5. E
    A standard Amazon SQS queue to buffer requests that require strict sequential processing.

Answer

The correct options are the use of AWS Lambda for short-lived backend logic, and Amazon DynamoDB in on-demand capacity mode for storing registration details.
AWS Lambda and Amazon DynamoDB in on-demand capacity mode together form a fully serverless backend. Both services automatically scale to zero when there is no traffic, ensuring no compute or write/read database capacity charges are incurred during inactive periods, and scale instantly to handle spikes.

Step-by-Step Solution

1
Analyze the workload requirements and identify that the traffic is highly unpredictable with long periods of complete inactivity.
This requires compute and database services that scale down to zero when idle to minimize costs.
Designing for cost optimization requires avoiding provisioned resources that incur charges during idle times.
2
Evaluate the compute options for executing lightweight backend logic under these conditions.
AWS Lambda is selected because it scales automatically and charges only when the code runs, with no idle costs.
Traditional server-based options or continuous execution models would waste money during inactive periods.
3
Evaluate the database options to store registration details cost-effectively.
Amazon DynamoDB with on-demand capacity mode is selected because it scales instantly with traffic spikes and charges only for read/write requests, with no hourly provisioning costs.
Provisioned database capacity incurs ongoing charges regardless of actual utilization, violating the cost-optimization goal.

Key Concept

Serverless architectures dynamically scale compute and database resources to match demand, minimizing idle costs for spiky, unpredictable workloads.
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Serverless and Automated Scaling Architectures for Cost Efficiency