What it is: Automatically adjusts capacity (number of instances) based on demand.

What it’s for:

• Handle traffic spikes and reduce cost during low usage.
• Improve availability by replacing unhealthy instances.

Key ideas:

• Uses Auto Scaling Group (ASG)
• Scaling decisions based on metrics (CPU, requests, custom metrics).

Exam cues:

• “traffic varies, need automatic scaling” → Auto Scaling + ASG.

Hard words:

• *capacity* /kəˈpæsəti/: năng lực/tài nguyên
• *demand* /dɪˈmænd/: nhu cầu
• *metric* /ˈmetrɪk/: chỉ số đo