SaaS Unlocked: A Complete Guide to Building and Scaling Software-as-a-Service Products

Chapter 4: Technical Architecture & Development

🔹 1. Choosing the Right Tech Stack

Your tech stack directly impacts:

• Development speed
• Scalability
• Maintainability
• Hiring developers

✅ Recommended SaaS Stack (Modern & Scalable)

✅ Choose based on team familiarity, community support, and scalability needs.

🔹 2. Understanding SaaS Architecture

🔸 What Makes SaaS Different?

Unlike a single-user app, a SaaS needs to:

• Support multiple customers (tenants)
• Separate or share databases securely
• Manage user roles across accounts
• Handle subscriptions and feature tiers

✅ Multi-Tenant vs. Single-Tenant

✅ Most SaaS startups begin with multi-tenant architecture.

🔹 3. Basic Folder Structure (Full-Stack App)

/saas-app

│

├── /client         # Frontend (React/Next.js)

├── /server         # Backend (Express/Django)

├── /scripts        # Deployment/build tools

├── /db             # Migrations/seeders

└── /docs           # Internal product notes

🔹 4. Authentication & User Management

🔸 Roles You’ll Need

🔸 Token-Based Auth (JWT)

// Example Payload

{

  userId: "123",

  tenantId: "456",

  role: "admin"

}

Use access tokens + refresh tokens for scalable authentication.

✅ Auth Tools

• Firebase Auth – Easy setup, great for MVPs
• Auth0 – Enterprise-ready with social login
• Clerk/Supabase Auth – Modern + developer-friendly
• Custom JWT + Middleware – Full control (but requires effort)

🔹 5. Database Design for SaaS

✅ Sample Multi-Tenant Schema

🔸 Isolation Options

• Shared DB, shared schema (easiest)
• Shared DB, separate schemas
• Separate DBs per tenant (max isolation)

✅ Use tenant IDs in queries and secure every API endpoint via middleware guards.

🔹 6. API Design (REST or GraphQL)

Example REST Routes:

GET    /api/tenants/:id/projects

POST   /api/tenants/:id/invite

PUT    /api/users/:id

Add tenant validation and role checking in middleware.

🔹 7. Payment Integration (Stripe)

Stripe is the go-to platform for SaaS subscriptions.

🔸 Key Features to Implement

✅ Stripe Webhook Example (Node.js)

app.post('/webhook', express.raw({ type: 'application/json' }), (req, res) => {

  const event = JSON.parse(req.body);

  if (event.type === 'invoice.payment_succeeded') {

    // Update user's subscription

  }

  res.send();

});

✅ Keep webhooks secure and idempotent.

🔹 8. Rate Limiting, Logging & Security

🔹 9. DevOps & CI/CD Overview

✅ Set up staging environments before production rollouts.

✅ Recap Table: Technical SaaS Foundations