How Alibaba’s Two‑Region Three‑Center Design Achieves 99.99% Availability

In Alibaba’s distributed architecture evolution, the “two‑region three‑center” (两地三中心) model serves as the foundational solution for financial‑grade high availability (HA) and continuous business operation.

“Two regions” refers to two far‑apart cities or areas—commonly East China paired with South China or North China—so that a single regional disaster (e.g., flood, earthquake) cannot cripple the whole system.

“Three centers” consist of:

Primary center : the main data‑processing hub handling daily business traffic.

Backup center : located in a different region, equipped with full business‑processing capability.

Remote disaster‑recovery center : the farthest site, activated only for major catastrophes.

Incoming user requests enter through a unified traffic gateway, are distributed to the two geographic locations (A and B), and then routed to the three logical centers (primary, backup, DR) as illustrated by the following diagram:

<ol><li>用户访问</li><li>|</li><li>统一流量入口</li><li>|</li><li>地点 A            地点 B</li><li>+--------+   +--------+</li><li>|中心1|------|中心2|------|灾备/双活|</li><li>+--------+   +--------+</li><li>|同城中心3|</li></ol>

This geographically dispersed design mitigates risks from single‑machine failures up to whole‑city natural disasters, enabling active‑active or active‑passive configurations that collectively achieve the target 99.99% availability.