How I Built a SaaS MVP in 24 Hours Using AI (Step-by-Step Guide)

TL;DR

You can go from zero to a deployed, payment-enabled SaaS MVP in 24 hours. Not a toy — a real product with auth, database, Stripe billing, and a landing page. Here's the hour-by-hour breakdown and every tool I used.

Total cost: ~$60 (mostly domain + first month of services) Stack: Next.js + Supabase + Stripe + Cloudflare, built with Claude Code and Cursor, deployed with Y Build.

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Why This Is Possible Now

Two years ago, building an MVP in 24 hours meant cutting corners everywhere — no auth, no payments, no real backend. You'd ship a static page and call it an MVP.

In 2026, AI coding tools have changed the math. Claude Code writes production-quality backend logic. Cursor handles frontend iteration at conversation speed. Y Build deploys to edge infrastructure with zero DevOps. The bottleneck isn't coding anymore — it's deciding what to build.

This guide documents the exact process, hour by hour.

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Hour 1-2: Idea Validation (Don't Skip This)

The biggest mistake in 24-hour builds is starting to code immediately. Two hours of validation saves you from building something nobody wants.

What I did

1. Problem identification — Browsed Reddit, Indie Hackers, and X for complaints about existing tools. Found a recurring pain point: freelancers struggling to track time across multiple clients without switching between 5 different apps.

1. Quick competitive analysis — Searched for existing solutions. Found Toggl, Harvest, Clockify. All focused on teams. None had a dead-simple "freelancer-first" mode with automatic invoicing.

1. Landing page test — Used Claude Code to generate a one-page landing page in 15 minutes. Added a "Join waitlist" button with a simple email capture form. Posted it to 3 relevant subreddits and 2 Slack communities.

1. Validation signal — Within 2 hours, had 23 email signups and 4 DMs asking "when does this launch?" That's enough signal.

Tools used

• Claude Code (landing page generation)
• Supabase (email capture — just a single table)
• Reddit, Indie Hackers (distribution)

Cost: $0

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Hour 3-6: Build the Core Product

This is where AI coding tools earn their keep. Four hours to build a functional SaaS app.

Hour 3: Project setup and data model

Opened Claude Code and described the product:

"Build a Next.js 15 app with Supabase auth and database. The app is a freelancer time tracker. Data model: users, clients, projects, time_entries, invoices. Time entries have start/stop timestamps and belong to a project. Projects belong to a client. Invoices aggregate time entries by client for a date range."

Claude Code generated the complete data model, Supabase migrations, and auth setup in one pass. I reviewed the schema, made two small adjustments (added a hourly_rate field to projects, added a status enum to invoices), and ran the migrations.

Time: 40 minutes

Hour 4-5: Core features

Switched to Cursor for frontend iteration. Built three screens:

1. Timer screen — Start/stop timer, select client and project, see today's total. Used Cursor's inline editing to iterate on the UI rapidly. Started with a basic layout, then refined spacing, colors, and micro-interactions through conversation.

1. Dashboard — Weekly summary, per-client breakdown, chart showing hours by day. Claude Code generated the data aggregation queries. Cursor handled the chart component.

1. Invoice generator — Select client, date range, generate PDF invoice. Used Claude Code for the PDF generation logic (html-to-pdf via Puppeteer-style rendering on the server).

Time: 2 hours

Hour 5-6: Polish and edge cases

• Added error handling and loading states
• Mobile responsive layout (Cursor made this fast — just described what should change at each breakpoint)
• Empty states for new users
• Onboarding flow: first-time users get prompted to add their first client

Time: 1 hour

Tools used

• Claude Code (backend logic, data model, API routes, PDF generation)
• Cursor (frontend UI iteration, responsive design)
• Next.js 15, Supabase, Tailwind CSS

Cost: $0 (free tiers)

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Hour 7-8: Deploy with Y Build

This used to be the painful part. Setting up CI/CD, configuring environment variables, DNS, SSL, CDN — easily a full day of DevOps work.

What I did

1. Connected repo — Linked the GitHub repo to Y Build. Auto-detected Next.js, suggested Cloudflare Workers deployment.

1. Environment variables — Y Build pulled the required env vars from my .env.local and prompted me to confirm each one for production. Added Supabase URL, anon key, and service role key.

1. Custom domain — Bought a domain ($12), pointed DNS to Y Build's nameservers. SSL provisioned automatically.

1. Deploy — One click. Y Build built the project, optimized assets, deployed to Cloudflare's edge network across 300+ locations. Total deploy time: 90 seconds.

1. AI SEO setup — Y Build auto-generated meta tags, Open Graph images, and a sitemap based on the app's pages. Added structured data for the landing page.

Time: 45 minutes (including the 20 minutes waiting for DNS propagation)

Tools used

• Y Build (deployment, DNS, SSL, SEO)
• Cloudflare (edge hosting via Y Build)

Cost: $12 (domain)

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Hour 9-12: Add Payments and Launch Prep

Hour 9-10: Stripe integration

Used Claude Code to add Stripe:

• Pricing page — Two tiers: Free (3 clients, basic timer) and Pro ($12/mo — unlimited clients, invoicing, reports)
• Checkout flow — Stripe Checkout session creation, webhook handling for subscription events
• Billing portal — Customer self-service for plan changes and cancellations
• Feature gating — Middleware to check subscription status and limit features for free users

Claude Code handled the entire Stripe integration — webhook signature verification, subscription lifecycle management, customer portal setup. I reviewed the webhook handler carefully (this is where money bugs live) and made one fix to handle the customer.subscription.updated event properly. Time: 1.5 hours

Hour 10-11: Landing page upgrade

Replaced the validation landing page with a proper one:

• Hero section with a product screenshot (took a screenshot of the running app)
• Feature grid with icons
• Pricing table
• FAQ section
• Social proof (used the 23 waitlist signups as "23 freelancers already waiting")

Used Cursor for rapid iteration on copy and layout. Claude Code generated the FAQ content based on the product features. Time: 1 hour

Hour 11-12: Product demo video

Used Y Build Demo Cut to generate a product demo video:

1. Pointed Demo Cut at the deployed app URL
2. AI walked through the app — timer, dashboard, invoice generator
3. Generated a 60-second demo with voiceover, transitions, and background music
4. Exported for Product Hunt gallery and landing page hero

Time: 10 minutes

Remaining time: wrote Product Hunt listing copy, prepared social media posts, set up analytics via Y Build's built-in dashboard.

Tools used

• Claude Code (Stripe integration)
• Cursor (landing page)
• Y Build Demo Cut (product demo video)
• Stripe

Cost: $0 (Stripe charges on transactions, no upfront cost)

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Hour 13-18: Launch

Product Hunt submission

• Uploaded the demo video, screenshots, and listing copy
• Scheduled launch for 12:01 AM PT (optimal timing)
• Prepared a "maker comment" explaining the 24-hour build story

Social media blitz

• Posted the build story on X with screenshots of each stage
• Shared in 5 relevant Slack communities (freelancer groups, indie hacker groups)
• Posted to r/SaaS, r/Freelance, and r/SideProject
• Sent an email to the 23 waitlist signups: "It's live. You're the first to know."

Results by hour 18

• 47 Product Hunt upvotes
• 120 unique visitors
• 8 signups (free tier)
• 2 Pro conversions ($24 MRR)

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Hour 19-24: Iterate on Feedback

First users surfaced three issues:

1. Timer didn't persist across page refreshes — Claude Code fixed this in 10 minutes (stored timer state in localStorage + synced with server)
2. Invoice PDF formatting broke on long project names — 5-minute CSS fix
3. Users wanted a "quick add" for time entries without using the timer — Claude Code built a manual entry form in 20 minutes

Deployed fixes via Y Build — each deploy took under 2 minutes.

By hour 24:

• 12 total signups


• 3 Pro conversions ($36 MRR)


• Core product stable and usable

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Complete Cost Breakdown

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What I'd Do Differently

1. Spend 30 more minutes on the data model — I had to add two fields later that would have been obvious with more upfront thinking. AI is fast at generating code, but it can't validate your business logic.

1. Set up analytics earlier — I didn't add event tracking until hour 15. Missed data on early user behavior.

1. Pre-write the Product Hunt listing — I scrambled to write copy at hour 11. Should have drafted it during the validation phase.

1. Test Stripe webhooks more thoroughly — Had a brief scare at hour 16 when a subscription update webhook failed silently. Always test the full subscription lifecycle before launch.

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The 2026 AI SaaS Stack

If you're building a SaaS MVP today, here's the stack I'd recommend:

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FAQ

Do I need to be a developer to do this? You need basic technical literacy — understanding of what a database is, what an API does, how web apps work. But you don't need to write code from scratch. Claude Code and Cursor handle the implementation. You're the product manager. What if my idea doesn't get validated in 2 hours? Kill it. The point of the 24-hour constraint is to move fast. If 2 hours of validation shows no interest, pick a different idea. You can always come back. Is a 24-hour MVP actually usable? Yes, if you scope ruthlessly. The secret is solving one problem well, not building a feature-complete product. My time tracker does three things: track time, show a dashboard, generate invoices. That's it. How do I handle scaling if it takes off? Supabase and Cloudflare (via Y Build) handle significant traffic out of the box. You won't hit scaling issues until thousands of daily active users. At that point, you'll have revenue to invest in infrastructure. What about mobile? Responsive web first. A dedicated mobile app is a Week 2 problem — after you've validated that people actually use the product.

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