Cost-Effective Serverless Reporting with AWS Lambda

SAA-C03 By islever Editorial Last updated

Design cost-optimized compute solutions.

Short answer

B Run the program in AWS Lambda triggered by EventBridge to minimize cost and management overhead for infrequent, short tasks.

Question

A company wants to analyze and generate reports to track the usage of its mobile app. The app is popular and has a global user base. The company uses a custom report building program to analyze application usage. The program generates multiple reports during the last week of each month. The program takes less than 10 minutes to produce each report. The company rarely uses the program to generate reports outside of the last week of each month The company wants to generate reports in the least amount of time when the reports are requested. Which solution will meet these requirements MOST cost-effectively?
  1. Run the program by using Amazon EC2 On-Demand Instances. Create an Amazon EventBridge rule to start the EC2 instances when reports are requested. Run the EC2 instances continuously during the last week of each month.
  2. Run the program in AWS Lambda. Create an Amazon EventBridge rule to run a Lambda function when reports are requested. Correct Answer
  3. Run the program in Amazon Elastic Container Service (Amazon ECS). Schedule Amazon ECS to run the program when reports are requested.
  4. Run the program by using Amazon EC2 Spot Instances. Create an Amazon EventBndge rule to start the EC2 instances when reports are requested. Run the EC2 instances continuously during the last week of each month.

Key Takeaways

Tests the ability to identify serverless options for infrequent workloads while avoiding infrastructure management overhead and interruption risks.

This question evaluates designing cost-optimized compute solutions for sporadic, short-duration tasks using AWS Lambda versus EC2 or ECS.

Common mistake: Choosing EC2 Spot Instances (D) due to lower hourly costs, ignoring that spot interruptions can delay critical monthly reports, or choosing ECS (C) which adds unnecessary complexity and cost for simple scripts.

Expert Analysis

Why the Answer Is Correct

The correct answer is B because AWS Lambda is designed for event-driven, short-running code execution without managing servers. Since the report generation takes less than 10 minutes and occurs only during a specific week each month, Lambda’s pay-per-use pricing model is significantly more cost-effective than keeping any infrastructure running continuously. It also provides the fastest startup time among the options, meeting the requirement for immediate report generation.

Why the Other Options Are Wrong

Option A (EC2 On-Demand) and Option D (EC2 Spot) are incorrect because they involve managing instances. While Spot is cheaper, it can be interrupted, risking delayed reports. Running them "continuously" during the last week of the month is wasteful and complex compared to Lambda. Option C (ECS) is valid but over-engineered; it requires setting up clusters, task definitions, and potentially paying for Fargate or EC2 capacity providers, which is more costly and complex than a simple Lambda function for this workload.

Community Comment Notes

Most learners correctly identified Lambda as the best fit. One user noted, "No infrastructure to manage. Love it," highlighting the operational simplicity. Another argued against ECS, stating it is "more cost more than B and is more complex." A dissenting view suggested Lambda might be too slow for multiple reports totaling over 10 minutes, but this overlooks Lambda's concurrency limits and typical cold start improvements, making it still the most efficient choice for this scale.

Exam Strategy

Always look for 'infrequent' or 'sporadic' triggers combined with short execution times (< 15 mins). These are prime indicators for AWS Lambda. Avoid managed services like ECS unless the workload requires long-running processes or specific container dependencies.

Frequently Asked Questions

Why not use EC2 Spot Instances for lower cost?

Spot Instances can be interrupted with short notice. For monthly reports where timing matters, interruptions could cause delays or failures, making Lambda's reliability superior.

Is Lambda too expensive if reports take 10+ minutes total?

Lambda charges per millisecond of execution. Even for multiple reports totaling ~30 minutes, the cost is negligible compared to paying for always-on EC2 or ECS instances.

More SAA-C03 FAQ →

Community Votes

B
82%
C
18%

82% of anonymous learners picked answer B. Votes are pick records left by other test-takers — they are not the verified answer.

Discussion 7 contributions

Compiled from public community threads and reader submissions, lightly edited for clarity. Handles and vote tallies are shown as recorded, and comments reflect the views of individual contributors.

From public community threads 7

  1. Scheldon 👍 2 Answered C
    AnswerC Option A and D are saying abount Running the EC2 instances countinously during the last week of each month which is not necessery from my understanding and will be not so cheap. Option B - 10min per report and we have couple of reports. So it looks like program is running for at least 20 min so in theory Lambda is not useful here Option C - ECS is allowing us to run Fargate which will allow to run program for more then 15 min, hence all reports which program is preparing should be created. I'm not sure but I think ECS API is allowing to run task on demand/request.
  2. EdricHoang 👍 2 Answered B
    "The program takes less than 10 minutes to produce each report. The company rarely uses the program to generate reports outside of the last week of each month The company wants to generate reports in the least amount of time when the reports are requested." I go for B because of this
  3. LeonSauveterre 👍 1 Answered B
    A - The task only runs for 10 minutes per report. Why would you need an EC2 instance? B - No infrastructure to manage. Love it. C - Works, but cost more than B and is more complex to set up than B. D - More cost-effective than A, but spot instances can be interrupted, probably causing delays in report generation.
  4. Andy_09 👍 6
    Option B
  5. asdfcdsxdfc 👍 2 Answered B
    B is corre ct
Show 2 more comments
  1. agbor_tambe 👍 2 Answered B
    B is correct
  2. NayeraB 👍 2 Answered B
    B..maybe?

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