Reference: B2B SaaS API

┌─────────────┐     ┌──────────────┐     ┌─────────────┐
│  ALB/Ingress│────▶│ orders-api   │────▶│ Postgres 16 │
│  + WAF      │     │ Nest+Fastify │     │ (tenant_id) │
└─────────────┘     └──────┬───────┘     └─────────────┘
                           │
                    ┌──────▼───────┐     ┌─────────────┐
                    │ Redis        │────▶│ order-worker│
                    │ cache+queue  │     │ BullMQ      │
                    └──────────────┘     └─────────────┘
                           │
                    ┌──────▼───────┐
                    │ OTel Collector│
                    └──────────────┘

src/
├── modules/
│   ├── orders/
│   │   ├── orders.controller.ts
│   │   ├── orders.service.ts
│   │   └── orders.repository.ts
│   ├── tenants/
│   └── webhooks/
├── common/
│   ├── guards/tenant.guard.ts
│   ├── interceptors/logging.interceptor.ts
│   └── prisma/prisma.service.ts
└── main.ts

// src/common/guards/tenant.guard.ts
@Injectable()
export class TenantGuard implements CanActivate {
  canActivate(ctx: ExecutionContext): boolean {
    const req = ctx.switchToHttp().getRequest();
    const tenantId = req.headers["x-tenant-id"] as string;
    if (!tenantId) throw new UnauthorizedException("Missing tenant");
    req.tenantId = tenantId;
    return true;
  }
}

// src/modules/orders/orders.service.ts - tenant-scoped queries
@Injectable()
export class OrdersService {
  constructor(private prisma: PrismaService) {}
 
  list(tenantId: string) {
    return this.prisma.order.findMany({
      where: { tenantId },
      take: 100,
    });
  }
}

# k8s/deployment.yaml (excerpt)
resources:
  requests: { cpu: "500m", memory: "512Mi" }
  limits:   { cpu: "2", memory: "768Mi" }
env:
  - name: NODE_OPTIONS
    value: "--max-old-space-size=512"
  - name: OTEL_SERVICE_NAME
    value: orders-api

// Trace propagation into BullMQ job data
await this.queue.add("order.created", payload, {
  headers: { traceparent: getCurrentTraceparent() },
});