How Alex Finn built a $300K ARR app solo using AI coding tools

Executive overview

Most developers assume building a serious software product requires a team. Alex Finn built, launched, and scaled a $300K ARR SaaS app entirely alone, with no prior coding background, using AI tools to write every line of code.

Distribution — not product — is the moat in a world where anyone can build anything with AI.

Building with Cursor and Windsurf

• Break every feature into the smallest possible sub-tasks before prompting the AI.
• First request: build the input. Second: build the button. Third: wire in the AI model — never all at once.
• Use ChatGPT to decompose a feature into micro-steps, then feed those steps into the coding tool.
• Smaller prompts produce faster results with fewer bugs.
• Alex switched from Cursor to Windsurf after perceiving a quality drop in October 2024.
• Uses ChatGPT o3 as a product manager throughout the build process.

Finding the idea

• Solve your own problem first; if you have the problem, others likely do too.
• Alex tracked tweets in a spreadsheet nightly to identify what worked — then built software to automate that process.
• Worst case: you've made your own life easier. Best case: you have a product.

Building an audience before launch

• Alex spent three years creating content on X before launching anything.
• A thread on the open-sourced X algorithm went viral; Elon Musk retweeted it, giving him hundreds of thousands of followers.
• Spent six to seven months iterating in public, sharing progress with his community.
• 150 beta testers before launch; met with each one individually to gather feedback.
• Beta tested until the day before launch (January 24, 2025).

Launch day execution

• Announced the launch date 12 days in advance (January 12).
• Ran a live Spaces session on X on launch day to build real-time momentum.
• Hit $100K ARR within 15 minutes; $200K ARR within two hours.
• Launch was not flawless — bugs surfaced immediately and had to be fixed solo.

Tech stack and unit economics

• Windsurf for coding, Vercel for hosting (Next.js), Supabase for data.
• Claude and ChatGPT APIs for AI features; Resend for email.
• X API: $5,000/month — the dominant cost.
• Total costs: ~$5,300/month on ~$25,000/month revenue → ~80% margins.

Key lessons

• Default response to any challenge: "just figure it out" — go to AI before hiring anyone.
• Knowledge and product quality are no longer defensible moats; distribution is.
• Someone can clone your app in hours, but they can't clone your audience.
• Stop overthinking what to build or tweet — take action, observe what works, adjust.
• Five to ten minutes of daily action compounds faster than waiting for the perfect plan.