Multi-Region Inference Architecture

System Diagram

                         MULTI-REGION INFERENCE ARCHITECTURE
═══════════════════════════════════════════════════════════════════════════════

                                    USERS
                                      │
                                      ▼
                          ┌───────────────────────┐
                          │    Global Load        │
                          │     Balancer          │
                          │   (Cloudflare)        │
                          │                       │
                          │  • Geo-DNS routing    │
                          │  • Health checks      │
                          │  • DDoS protection    │
                          └───────────┬───────────┘
                                      │
              ┌───────────────────────┼───────────────────────┐
              │                       │                       │
              ▼                       ▼                       ▼
┌─────────────────────┐ ┌─────────────────────┐ ┌─────────────────────┐
│      US-WEST        │ │      US-EAST        │ │      EU-WEST        │
│    (us-west-2)      │ │    (us-east-1)      │ │   (eu-west-1)       │
└──────────┬──────────┘ └──────────┬──────────┘ └──────────┬──────────┘
           │                       │                       │
           ▼                       ▼                       ▼
┌─────────────────────┐ ┌─────────────────────┐ ┌─────────────────────┐
│    API Gateway      │ │    API Gateway      │ │    API Gateway      │
│      (Kong)         │ │      (Kong)         │ │      (Kong)         │
│                     │ │                     │ │                     │
│ • Rate limiting     │ │ • Rate limiting     │ │ • Rate limiting     │
│ • Auth              │ │ • Auth              │ │ • Auth              │
│ • Request routing   │ │ • Request routing   │ │ • Request routing   │
└──────────┬──────────┘ └──────────┬──────────┘ └──────────┬──────────┘
           │                       │                       │
           ▼                       ▼                       ▼
┌─────────────────────┐ ┌─────────────────────┐ ┌─────────────────────┐
│     vLLM Pool       │ │     vLLM Pool       │ │     vLLM Pool       │
│     (4x A100)       │ │     (4x A100)       │ │     (4x A100)       │
│                     │ │                     │ │                     │
│ Models:             │ │ Models:             │ │ Models:             │
│ • LLaMA 3.1 70B     │ │ • LLaMA 3.1 70B     │ │ • LLaMA 3.1 70B     │
│ • Mistral 7B        │ │ • Mistral 7B        │ │ • Mistral 7B        │
└──────────┬──────────┘ └──────────┬──────────┘ └──────────┬──────────┘
           │                       │                       │
           ▼                       ▼                       ▼
┌─────────────────────┐ ┌─────────────────────┐ ┌─────────────────────┐
│     Vector DB       │ │     Vector DB       │ │     Vector DB       │
│     (Milvus)        │ │     (Milvus)        │ │     (Milvus)        │
│                     │ │                     │ │                     │
│   Read Replica      │ │     PRIMARY         │ │   Read Replica      │
└──────────┬──────────┘ └──────────┬──────────┘ └──────────┬──────────┘
           │                       │                       │
           └───────────────────────┼───────────────────────┘
                                   │
                          ┌────────┴────────┐
                          │   Replication   │
                          │    < 30s lag    │
                          └─────────────────┘

                                   │
                                   ▼
                    ┌─────────────────────────────┐
                    │     FALLBACK: Claude API    │
                    │   (when self-hosted full)   │
                    └─────────────────────────────┘

Mermaid Diagram (for rendered viewing)

flowchart TB
    Users["👥 Users"] --> GLB["Global Load Balancer<br/>Cloudflare"]

    GLB --> USW["US-WEST"]
    GLB --> USE["US-EAST"]
    GLB --> EU["EU-WEST"]

    subgraph USW["US-WEST (us-west-2)"]
        APIGW1["API Gateway"] --> VLLM1["vLLM Pool<br/>4x A100"]
        VLLM1 --> VDB1[("Vector DB<br/>Read Replica")]
    end

    subgraph USE["US-EAST (us-east-1)"]
        APIGW2["API Gateway"] --> VLLM2["vLLM Pool<br/>4x A100"]
        VLLM2 --> VDB2[("Vector DB<br/>PRIMARY")]
    end

    subgraph EU["EU-WEST (eu-west-1)"]
        APIGW3["API Gateway"] --> VLLM3["vLLM Pool<br/>4x A100"]
        VLLM3 --> VDB3[("Vector DB<br/>Read Replica")]
    end

    VDB2 -.->|"Replication<br/>less than 30s lag"| VDB1
    VDB2 -.->|"Replication<br/>less than 30s lag"| VDB3

    USW & USE & EU -.->|"Fallback when<br/>self-hosted full"| Claude["Claude API<br/>Fallback"]

    style USW fill:#e3f2fd
    style USE fill:#e8f5e9
    style EU fill:#fff3e0

Routing Logic

Step	Condition	Action
1	Default	Geo-DNS routes to nearest region
2	Region unhealthy	Failover to next nearest region
3	Region >80% utilized	Overflow to another region
4	EU user	Force EU-WEST only (GDPR)
5	All self-hosted exhausted	Fallback to Claude API

Key Metrics Per Region

Metric	Description	Alert Threshold
Request latency	P50/P95/P99	P95 > 3s
GPU utilization	% of compute used	> 85% sustained
Queue depth	Pending requests	> 100
Error rate	Failed requests	> 1%
Replication lag	Vector DB sync delay	> 30s

Regional Failover Sequence

US-WEST user request:
  1. Try US-WEST (primary)
  2. If unavailable → US-EAST (secondary)
  3. If unavailable → EU-WEST (tertiary, higher latency)
  4. If all unavailable → Claude API fallback

EU user request (GDPR):
  1. Try EU-WEST only
  2. If unavailable → Claude API (EU endpoint)
  3. Never route to US regions