Question

Difficulty: MediumCost-Optimized Compute Selection and Purchasing Strategies

A logistics company is designing a new package tracking system on AWS. The application consists of a microservices-based API layer hosted on AWS Fargate that handles consistent, steady-state transaction volume 24/724/7, and a relational database layer running on Amazon RDS for PostgreSQL that operates continuously to store tracking history. Additionally, an hourly background job aggregates tracking metrics, running continuously for 5050 minutes of every hour. The company wants to minimize compute costs for this architecture while maintaining high availability and performance. Which TWO purchasing strategies or configurations should a solutions architect recommend? (Select two.)

  1. Purchase a Compute Savings Plan to cover the AWS Fargate API layer.Answer
  2. Purchase Amazon RDS Reserved Instances to cover the PostgreSQL database.Answer
  3. C
    Increase the Compute Savings Plan commitment size to cover both the Fargate API layer and the Amazon RDS database instances.
  4. D
    Migrate the 5050-minute hourly background job to AWS Lambda functions to eliminate idle compute costs.
  5. E
    Migrate the tracking history database to Amazon DynamoDB configured with Provisioned Capacity Mode to handle highly unpredictable, spiky query volumes.

Answer

Purchase a Compute Savings Plan to cover the AWS Fargate API layer, and purchase Amazon RDS Reserved Instances to cover the PostgreSQL database.
Purchasing a Compute Savings Plan is the most cost-effective option for the Fargate API layer because it offers discounts up to 66%66\% on EC2, Fargate, and Lambda for a 11- or 33-year commitment. Since Compute Savings Plans do not cover Amazon RDS, purchasing RDS Reserved Instances is the correct and separate method to optimize costs for the database layer.

Step-by-Step Solution

1
Analyze the steady-state API layer hosted on AWS Fargate.
Determine that Compute Savings Plans apply directly to AWS Fargate, providing flexible discounts for steady-state container workloads.
Fargate is a supported compute type under Compute Savings Plans.
2
Analyze the database layer hosted on Amazon RDS.
Identify that Amazon RDS Reserved Instances are the appropriate vehicle for discounting continuous database workloads, since Compute Savings Plans do not apply to RDS.
Compute Savings Plans are restricted to EC2, Fargate, and Lambda.
3
Evaluate the 5050-minute hourly background job.
Keep the job on Fargate or EC2 rather than migrating to AWS Lambda.
AWS Lambda's maximum execution duration of 1515 minutes prevents it from running a 5050-minute job, and continuous execution on Lambda is cost-prohibitive.

Key Concept

Selecting cost-optimized compute options by matching workloads to appropriate purchasing plans (Compute Savings Plans for Fargate, RDS Reserved Instances for databases) and avoiding platform limitations (Lambda timeout limits).
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