AWS Solutions Architect Associate

Compute

⏱ ~4-min readAceMark Guide

The big idea

What this topic is really about

Amazon ECS on Fargate abstracts away the underlying EC2 instances, allowing you to run containers without managing servers or clusters. You define task definitions and the service handles provisioning, scaling, and patching of the compute resources. This reduces operational complexity while still providing the performance and isolation needed for web workloads.

An Auto Scaling lifecycle hook on the EC2_INSTANCE_LAUNCHING transition pauses the instance after launch but before it is attached to the load balancer, allowing you to run custom scripts. The TERMINATING transition is for shutdown, instance refresh controls replacement cycles, and scheduled scaling is time‑based, not event‑driven.

How it works

See the mechanism

Diagram coming soon

AWS Auto Scaling monitors your applications and automatically adjusts Amazon EC2 capacity to maintain steady, predictable performance at the lowest possible cost. A diagram for this topic isn't available yet — the worked example below walks the same reasoning step by step.

Worked example

An exam-style question, fully explained

Which AWS service automatically scales EC2 capacity in response to demand?

Identify what the question tests: Which AWS service automatically scales EC2 capacity in response to demand.
AWS Auto Scaling monitors your applications and automatically adjusts Amazon EC2 capacity to maintain steady, predictable performance at the lowest possible cost.
AWS Lambda (Option A) is a serverless compute service that runs code in response to events, rather than managing and scaling EC2 instances directly.

Answer:AWS Auto Scaling

Common mistakes

Traps the examiner sets

On-Demand instances are much more expensive and unnecessary for workloads that do not require continuous, uninterrupted runtime.
The R5 family provides a high memory-to-CPU ratio, making it ideal for memory‑intensive workloads such as in‑memory databases or analytics that do not need high compute power.

Self-check

Test your recall

Answer each from memory — you'll see instantly whether you're right and why.

Q1.Which AWS service automatically scales EC2 capacity in response to demand?

Q2.Cost-effective option for a fault-tolerant batch workload:

Q3.To trigger a Lambda function on S3 object creation, configure:

Q4.You need to perform custom actions when an Auto Scaling group launches a new EC2 instance, but you want the instance to be fully registered with a load balancer before the action runs. Which feature should you use?

Q5.You need to run a containerized web application with minimal operational overhead. Which service should you choose?

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