What it is: An Auto Scaling behavior that maintains balanced instance distribution across enabled Availability Zones.

What it’s for:

• Keep capacity balanced across AZs for better availability.
• Recover from manual termination or AZ capacity differences.

Key exam fact:

• During rebalancing, Auto Scaling launches new instances before terminating old ones to avoid impacting availability.

Hard words (English + IPA + Vietnamese meaning):

• *rebalance* /ˌriːˈbæl.əns/: cân bằng lại
• *unbalanced* /ʌnˈbælənst/: bị lệch/mất cân bằng
• *availability* /əˌveɪləˈbɪləti/: tính sẵn sàng