Routing System Design

4.1 DNS and Endpoint Strategy

┌─────────────────────────────────────────────────────────────────┐
│                     DNS STRUCTURE                                │
│                                                                  │
│  *.workloads.computearbitrage.com                               │
│     │                                                            │
│     ├── HTTP: {workload-id}.workloads.computearbitrage.com      │
│     │         Points to Cloudflare Workers                       │
│     │                                                            │
│     └── TCP:  tcp-{workload-id}.workloads.computearbitrage.com  │
│               Points to Spectrum application                     │
│                                                                  │
│  api.computearbitrage.com                                        │
│     └── Control plane API (Workers)                              │
│                                                                  │
│  console.computearbitrage.com                                    │
│     └── Web console (Workers + Assets)                           │
└─────────────────────────────────────────────────────────────────┘

4.2 HTTP Routing Flow

┌──────────┐     ┌─────────────────┐     ┌──────────────┐     ┌─────────────┐
│  Client  │────▶│ Cloudflare Edge │────▶│ HTTP Router  │────▶│  Workload   │
│          │     │   (Anycast)     │     │  (Worker)    │     │  Instance   │
└──────────┘     └─────────────────┘     └──────────────┘     └─────────────┘
                                                │
                                                ▼
                                         ┌──────────────┐
                                         │  KV Lookup   │
                                         │  (endpoint)  │
                                         └──────────────┘

Request Flow:

1. Client makes request to {workload-id}.workloads.computearbitrage.com
2. DNS resolves to nearest Cloudflare edge (anycast)
3. HTTP Router Worker intercepts request
4. Worker extracts workload ID from subdomain
5. Worker validates JWT token from Authorization header
6. Worker looks up current endpoint in KV: workload:{id}:endpoint
7. Worker forwards request to actual workload instance
8. Response returned to client with latency <50ms added

4.3 TCP Routing Flow

┌──────────┐     ┌─────────────────┐     ┌──────────────┐     ┌─────────────┐
│  Client  │────▶│    Spectrum     │────▶│  Connection  │────▶│  Workload   │
│  (TCP)   │     │   (L4 Proxy)    │     │   Manager    │     │  Instance   │
└──────────┘     └─────────────────┘     │   (DO)       │     └─────────────┘
                                         └──────────────┘

Connection Flow:

1. Client opens TCP connection to tcp-{workload-id}.workloads.computearbitrage.com:PORT
2. Cloudflare Spectrum terminates connection at edge
3. Spectrum forwards connection metadata to Connection Manager Durable Object
4. DO looks up backend endpoint and validates token (passed in initial handshake)
5. DO returns backend endpoint to Spectrum
6. Spectrum proxies TCP traffic to workload instance
7. Connection state tracked in DO for graceful handling of backend changes

4.4 Routing Table Updates

When workload infrastructure changes (new instance, migration, etc.):

// routing-updater/src/index.ts
async function updateRouting(workloadId: string, newEndpoint: string): Promise<void> {
  // 1. Update KV (propagates globally in <60s, usually <1s)
  await env.ROUTING_KV.put(`workload:${workloadId}:endpoint`, newEndpoint);
  
  // 2. Update D1 for consistency
  await env.DB.prepare(`
    UPDATE workload_routing SET endpoint = ?, updated_at = ? WHERE workload_id = ?
  `).bind(newEndpoint, Date.now(), workloadId).run();
  
  // 3. Notify active TCP connections via Durable Object
  const connectionManager = env.CONNECTION_MANAGER.get(
    env.CONNECTION_MANAGER.idFromName(workloadId)
  );
  await connectionManager.notifyBackendChange(newEndpoint);
  
  // 4. Publish event to Queue for audit/analytics
  await env.EVENTS_QUEUE.send({
    type: 'ROUTING_UPDATED',
    workloadId,
    newEndpoint,
    timestamp: Date.now(),
  });
}