====== Availability Zone (AZ) ======

**What it is:** One or more data centers with independent power, cooling, and networking—inside a Region.

**What it’s for:**
  * Build **high availability** by spreading workloads across multiple AZs.
  * Reduce blast radius (a problem in one AZ should not take down everything).

**Key ideas:**
  * A Region has multiple AZs.
  * “Multi-AZ” usually means “across at least 2 AZs”.
  * AZs are connected with high-bandwidth, low-latency links.

**Common exam cues:**
  * “must survive an AZ outage” → design for [[aws:global:multi-az|Multi-AZ]].
  * “single AZ deployment risk” → add another AZ.

**Hard words:**
  * *availability* /əˌveɪləˈbɪləti/: tính sẵn sàng
  * *outage* /ˈaʊtɪdʒ/: sự cố mất dịch vụ
  * *blast radius* /blæst ˈreɪdiəs/: phạm vi ảnh hưởng
  * *bandwidth* /ˈbændwɪdθ/: băng thông