I shipped my first SaaS in a day — here's the stack, the costs, and what I learned

#webdev #startup #ai #beginners

I've been in analytics and business strategy for 13 years. I know Python. I understand data. I've made a career out of helping companies make smarter decisions.

But until last week, I'd never built anything for myself. Every side project got stuck in planning mode — researching, overthinking, waiting for the perfect moment that never came.

Last week I tried something different. No planning. No Notion docs. Just sit down and build.

What I built

A CSV analyzer. You upload a CSV file and it instantly gives you:

Column-level statistics (mean, median, std dev, unique values)
Interactive charts (histogram, scatter, bar with percentages)
AI-powered analysis that explains your data in plain English

Everything runs in the browser. Your data never gets uploaded to a server. The AI analysis sends only summary statistics to the backend, not your raw data.

The stack

Next.js — frontend and API routes
Anthropic API (Claude) — powers the AI analysis
Stripe — payment processing
Vercel — hosting (free tier)
Plotly — interactive charts

Total infrastructure cost: roughly $1/month.

Security considerations

Since users upload files and AI processes data, I had to think about:

Prompt injection: CSV cells could contain "ignore previous instructions" — I sanitize all data before it reaches the AI with regex filters for common injection patterns
XSS: React auto-escapes, but I also strip HTML tags and neutralize URLs in cell values
API key exposure: The Anthropic API is called server-side via a Next.js API route. The key never reaches the browser.
File bombs: 50MB file size cap, row/column limits per pricing tier, individual cells truncated to 500 characters
Rate limiting: In-memory rate limiter on the API route — 10 requests per minute per IP

Pricing model

Free: 500 rows, 20 columns, stats and charts only
Single Analysis ($2.99): 50K rows, 50 columns, one AI analysis
Pro ($9/month): 500K rows, 100 columns, unlimited AI analyses

The AI analysis costs me about $0.01-0.03 per request, so margins are strong even at $2.99.

First week results

127 visitors
$0 revenue
2 out of 3 Reddit posts got auto-rejected
0 comments on Hacker News
But real people visited and used the tool

Not glamorous. But it's real.

What I learned

The biggest obstacle wasn't technical. The code was the easy part. The hard part was not closing the laptop. Not switching to something easier. Not telling myself I'd do it tomorrow.

If you're stuck in planning mode — here's what worked for me: remove the gap between deciding and doing. Don't make a task list. Don't set up project management. Just open your editor and build the worst possible version. Ship it before your brain talks you out of it.

You can refine later. You can't refine something that doesn't exist.