Multi-Region & Disaster Recovery — Simple

flowchart LR
  U[Users worldwide]
  R1[Region A]
  R2[Region B]
  R3[Region C]
  GLB[Geo / latency LB]
  U --> GLB
  GLB --> R1
  GLB --> R2
  GLB --> R3
  R1 <-. async replication .-> R2
  R2 <-. async replication .-> R3

    classDef client fill:#dbeafe,stroke:#1e40af,stroke-width:1px,color:#0f172a;
    classDef edge fill:#cffafe,stroke:#0e7490,stroke-width:1px,color:#0f172a;
    classDef service fill:#fef3c7,stroke:#92400e,stroke-width:1px,color:#0f172a;
    classDef datastore fill:#fee2e2,stroke:#991b1b,stroke-width:1px,color:#0f172a;
    classDef cache fill:#fed7aa,stroke:#9a3412,stroke-width:1px,color:#0f172a;
    classDef queue fill:#ede9fe,stroke:#5b21b6,stroke-width:1px,color:#0f172a;
    classDef compute fill:#d1fae5,stroke:#065f46,stroke-width:1px,color:#0f172a;
    classDef storage fill:#e5e7eb,stroke:#374151,stroke-width:1px,color:#0f172a;
    classDef external fill:#fce7f3,stroke:#9d174d,stroke-width:1px,color:#0f172a;
    classDef obs fill:#f3e8ff,stroke:#6b21a8,stroke-width:1px,color:#0f172a;
    class GLB edge;
    class U,R1,R2,R3 service;

Make your system survive losing an entire region. Two axes: RTO (how fast can you recover?) and RPO (how much data can you lose?). Patterns range from cold standby (high RTO, high RPO) to active-active (RTO ≈ 0, RPO ≈ 0).