Certified Solutions Architect EC2 Instance Types and Cost Flashcards

A company is running a high-performance computing (HPC) workload for complex scientific simulations. The workload is CPU-bound and requires the best possible processor performance. Which EC2 instance family is the MOST cost-effective choice for this scenario?

Answer: Compute Optimized (C-series)

Compute Optimized (C-series) instances are designed for compute-intensive workloads and have a higher ratio of vCPUs to memory. They offer the lowest cost per vCPU, making them the most cost-effective choice for CPU-bound applications like HPC, batch processing, and video encoding.

A startup is launching a new web application with unpredictable traffic patterns. They need a flexible EC2 purchasing option that allows them to pay for compute capacity by the second with no long-term commitment. Which purchasing option should they choose?

Answer: On-Demand Instances

On-Demand Instances are ideal for short-term, spiky, or unpredictable workloads where you can't forecast compute needs. They offer the flexibility to pay for capacity by the hour or second with no upfront payment or long-term contract, which is perfect for a new application with unknown traffic.

A financial services company runs a critical, stateful application that must be available 24/7 for the next three years. The workload is stable and predictable. To achieve the highest possible discount on their EC2 costs, which purchasing option offers the best savings for this long-term, predictable workload?

Answer: EC2 Instance Savings Plans

EC2 Instance Savings Plans provide the deepest discounts (up to 72%) in exchange for a commitment to a specific instance family in a region for a 1 or 3-year term. Since the workload is stable and predictable, this model offers the highest savings compared to other flexible options like Compute Savings Plans or On-Demand pricing. Spot Instances are not suitable for critical, uninterruptible workloads.

A media company needs to run a large-scale video transcoding job. The job can be broken down into many parallel tasks, is fault-tolerant, and can be stopped and restarted without significant impact. The primary goal is to minimize the cost of this batch processing workload. Which EC2 purchasing model is the MOST suitable?

Answer: Spot Instances

Spot Instances offer the largest discounts on EC2, up to 90% off On-Demand prices, by allowing you to use spare AWS capacity. They are ideal for fault-tolerant, flexible workloads like batch processing, data analysis, and background tasks that can handle interruptions, as AWS can reclaim the instances with a two-minute warning.

A company is migrating a large in-memory database to AWS. The application requires extremely high memory performance to process large datasets in real-time. Which EC2 instance family is specifically designed for this type of workload?

Answer: Memory Optimized (R-series)

Memory Optimized instances, such as the R and X series, are designed for workloads that process large data sets in memory. They offer the lowest cost per GiB of RAM and are ideal for high-performance databases, distributed in-memory caches, and real-time big data analytics.

A company has a steady-state workload and wants to commit to a certain amount of compute usage (e.g., $10/hour) for a 1-year term to receive a discount. However, they need the flexibility to change instance families, sizes, and even regions over time. Which AWS purchasing option provides this level of flexibility while still offering significant savings over On-Demand pricing?

Answer: Compute Savings Plans

Compute Savings Plans offer significant discounts (up to 66%) in exchange for a commitment to a consistent amount of compute usage, measured in $/hour. They are the most flexible option, automatically applying to EC2 usage across different instance families, sizes, operating systems, tenancies, and AWS Regions. They also apply to AWS Fargate and Lambda usage.