Auto Scaling adds and removes EC2 instances automatically based on demand. Traffic spikes, it scales out; traffic drops, it scales back in so you’re not paying for idle servers. It’s half of the classic architect pairing: Auto Scaling for capacity, a load balancer to spread traffic across it.
Key ideas
A launch template defines new instances. Scaling policies decide when to add or remove them, usually off a CloudWatch metric. Set minimum, desired, and maximum counts to control the floor and ceiling. Auto Scaling also replaces unhealthy instances automatically.
Test yourself
An app gets slammed every weekday at 9 a.m. and sits idle overnight. You want to handle the morning load without paying for it at 3 a.m. What do you use?
- A single large EC2 instance running 24/7
- EC2 Auto Scaling with a scaling policy
- A bigger EBS volume
- Multi-AZ RDS
👉 Click to reveal the answer & explanation
Correct answer: B. Auto Scaling scales out for the morning rush and back in overnight, so you pay only for what you need. A fixed large instance (A) pays for idle capacity; storage (C) and database HA (D) don’t address compute demand.
Related topics
Amazon EC2 · Elastic Load Balancing · Amazon CloudWatch
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