Building a Working SaaS MVP in Three Days Using Claude Code
I used to spend weeks polishing features nobody had asked for. Last month I gave myself 72 hours, opened Cursor, and told Claude Code “build the smallest thing that proves people will pay for this.” The result was a working SaaS prototype with Stripe billing, user authentication, and a dashboard—deployed to Vercel before the weekend ended.
What Does a Focused MVP Actually Require?
The classic MVP playbook hasn’t changed: identify a real problem, define one core value proposition, and strip away everything else. What has changed is the speed of validation. AI coding tools compress the build‑measure‑learn loop from weeks to days.
My current validation stack
- Cursor — primary IDE, Cmd+K for inline edits, Composer for multi‑file features
- Claude Code — terminal agent for scaffolding, migrations, test generation
- v0.dev — instant UI components when I don’t want to write Tailwind
- Supabase — auth + database + edge functions in one PostgreSQL backend
- Vercel — zero‑config deploy, preview URLs for every push
3‑Day Sprint Breakdown
Day 1 – Validate the problem before writing code. I wrote a one‑pager, posted it in two relevant Discord servers, and received 12 people saying “shut up and take my money.” Only then did I open Cursor.
Day 2 – Scaffold → authenticate → charge. I gave Claude Code one prompt:
Create a Next.js 14 app with Supabase auth (email/password + OAuth),
a /dashboard route protected by middleware, and a Stripe Checkout
integration that creates a subscription on success. Use TypeScript,
Tailwind, and App Router. Output the full file tree.A working repository appeared in 45 minutes. The rest of the day was spent styling the pricing page and writing the webhook handler.
Day 3 – Polish the happy path. Loading states, error toasts, and the email confirmation flow were added. After deployment, the preview link was sent to the 12 people from Day 1; three converted to paid before Monday.
What I Skip Now, and You Should Too
- Custom UI component libraries — v0 + shadcn/ui covers 90 %
- Manual API route boilerplate — Supabase edge functions + generated types
- Test suites for throwaway code — E2E tests only for the payment flow
- Admin panels — SQL queries in the Supabase dashboard until revenue justifies them
The Trap to Avoid
AI makes overbuilding easier, not harder. In an afternoon you can generate a full admin dashboard, analytics pipeline, and notification system. Don’t. Every feature added before charging a single user is an untested hypothesis.
My rule now: one paid user > 100 GitHub stars. The code quality of the Day 2 scaffold was embarrassing—hard‑coded secrets, no tests, console logs everywhere—but it worked, and that was the only metric that mattered.
When an MVP Earns Architectural Complexity
The next sprint will replace the Stripe webhook with a proper event‑driven architecture using Upstash QStash, but only because MRR demands it.
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It’s wild how much technical debt can pile up in just 72 hours—imagine trying to build something solid under that pressure. I’ve seen it happen firsthand, but the real shift is how quickly you can validate demand now. For example, I once spent weeks refining features no one actually wanted, but last time I tried a different approach: I spent just a day drafting a one-pager outlining the problem, posted it in niche communities, and got 12 people saying they’d pay before writing a single line of code. That kind of early feedback saved me from chasing the wrong thing entirely. Now, the codebase might still need some cleanup, but at least it’s built on actual interest. How’s yours shaping up?
Fast shipping beats polish every time. Did you hit any major roadblocks in those 4 days? I started by giving myself 72 hours, opened Cursor, and told Claude Code "build the smallest thing that proves people will pay for this."
I used a concise deploy checklist—like verifying environment variables match your
.env.localfile before pushing—to avoid those Vercel env issues. Focused on the core value prop, I built a Next.js auth flow with Stripe integration directly from the prompt, then deployed to Vercel’s zero-config preview.