Edge-First Architectures: Latency as a Foundational Constraint

// Regional edge routing isolate
export default {
  async fetch(request: Request, env: Env): Promise<Response> {
    const clientRegion = request.cf?.colo || 'ORD';
    const sessionToken = request.headers.get('Authorization');
    
    // Validate cryptographically signed session locally at the edge
    const session = await verifyEdgeJwt(sessionToken, env.JWT_PUBLIC_KEY);
    if (!session) return new Response('Unauthorized', { status: 401 });

    // Read from regional read-replica KV store (sub-5ms)
    const cachedWorkspace = await env.EDGE_KV.get(`ws:${session.workspaceId}`, 'json');
    if (cachedWorkspace) {
      return Response.json(cachedWorkspace, {
        headers: { 'X-Edge-Hit': clientRegion, 'Cache-Control': 'private, max-age=60' }
      });
    }

    // Fallback to origin database only when cache misses occur
    return fetch(new Request(env.ORIGIN_URL, request));
  }
};