Exercise 09: Your Own SaaS — The Agentic Crew Hands-On Guide

Overview

Every chapter so far has been an exercise. This one is different. This is the real thing. You are going to build a product — a complete, publicly accessible micro-SaaS application — from scratch, in one chapter.

Not a tutorial project. Not a toy. Something with a URL you can text to a friend. Something that solves a real problem, accepts real users, and processes real payments. The AI agent is your co-founder for the day.

You are about to ask the agent to generate thousands of lines of code. Without a spec, it will make assumptions — and those assumptions will conflict with each other. A spec is not bureaucracy. It is the single source of truth that keeps you and the agent aligned across dozens of prompts.
— from the exercise

What you'll build

By the end of this exercise

✓ A full-stack Next.js application with TypeScript

✓ SQLite database with Prisma ORM

✓ User authentication (email/password with NextAuth.js)

✓ Stripe payment integration (free tier + paid tier)

✓ An AI-powered core feature using the Anthropic API

✓ Rate limiting (free users: 3/day, paid: unlimited)

✓ A landing page with SEO and social sharing meta tags

✓ CI/CD pipeline with GitHub Actions

✓ Deployed to production — a live URL anyone can visit

Key concepts

Terms you'll learn

Term What it means

SaaS Software as a Service — a web app users access via a browser, often with paid tiers

Full-stack Frontend (what users see) + backend (server logic) + database (data storage)

ORM Object-Relational Mapping — talk to your database using code instead of SQL

Authentication Proving who you are — login, sessions, password hashing

Webhook A URL that Stripe calls to notify your app when a payment event happens

Rate limiting Restricting how many times a user can do something (e.g., 3 AI requests per day)

Environment variables Secrets (API keys, database URLs) stored outside your code

What's covered

Sections in this exercise

01 What You'll Build

02 What You'll Need

03 Pick Your Idea

04 Scaffold the Full Stack

05 Add the AI Brain

06 Users, Auth, and Payments

07 Test It

08 Ship It

09 The Landing Page and Launch Checklist

10 Show Your Work

What just happened

You built a complete product — frontend, backend, database, auth, payments, AI features, CI/CD, and a landing page — and shipped it to a live URL. The agent was your co-founder. You brought the vision and the quality bar. It brought the implementation speed.