Resilient API Gateways & Backend-For-Frontend (BFF) Pattern

1// lib/bff/customer-portal.ts
2import 'server-only';
3
4interface CustomerDashboardDTO {
5  profile: { name: string; email: string };
6  billingStatus: 'active' | 'past_due' | 'unavailable';
7  recommendations: Array<{ id: string; title: string }>;
8}
9
10// Resilient fetch wrapper with timeout abort
11async function fetchWithTimeout(url: string, options: RequestInit = {}, timeoutMs = 2500) {
12  const controller = new AbortController();
13  const id = setTimeout(() => controller.abort(), timeoutMs);
14
15  try {
16    const res = await fetch(url, { ...options, signal: controller.signal });
17    return res;
18  } finally {
19    clearTimeout(id);
20  }
21}
22
23export async function getCustomerDashboardBFF(userId: string): Promise<CustomerDashboardDTO> {
24  // 1. Critical Service: User Profile (Must succeed)
25  const profilePromise = fetchWithTimeout(`https://internal-user-service/users/${userId}`)
26    .then(res => res.json());
27
28  // 2. Non-Critical Service: Billing (Has fallback if service is down)
29  const billingPromise = fetchWithTimeout(`https://internal-billing-service/status/${userId}`)
30    .then(res => res.json())
31    .catch((err) => {
32      console.warn('[BFF] Billing service degraded:', err.message);
33      return { status: 'unavailable' }; // Graceful degradation!
34    });
35
36  // 3. Non-Critical Service: Recommendation AI Engine
37  const recsPromise = fetchWithTimeout(`https://internal-ai-service/recs/${userId}`)
38    .then(res => res.json())
39    .catch(() => ({ items: [] })); // Fallback to empty list
40
41  // Execute in parallel
42  const [profile, billing, recs] = await Promise.all([
43    profilePromise,
44    billingPromise,
45    recsPromise,
46  ]);
47
48  // Aggregate and return clean frontend DTO
49  return {
50    profile: { name: profile.fullName, email: profile.primaryEmail },
51    billingStatus: billing.status,
52    recommendations: recs.items,
53  };
54}