I built a free DSA interview prep site because I was tired of the existing options

Piyush Hajare — Mon, 25 May 2026 14:37:05 +0000

So here's the thing - I've been prepping for DSA interviews on and off for like 2 years now. And every time I open up one of those big platforms (you know the ones), I get hit with this wall of 2000+ problems and immediately close the tab. Classic.

The problem isn't that those platforms are bad. They're great if you have months to grind. But most of us don't. We've got jobs, side projects, lives. What I actually needed was something that told me "hey, do THIS today, it'll take 15 minutes, and you'll actually learn something."

So I built it.

What is CrackCode?

CrackCode is a free DSA interview prep platform with a structured 30-day curriculum. Each day covers one topic with a short lesson and curated problems. The whole point is that you can do your daily prep while having your morning tea/coffee.

No account needed to browse the curriculum. Sign up if you wanna track your progress.

What it covers

The 30 days go through the standard stuff you'd expect:

Arrays, strings, hashmaps
Linked lists, stacks, queues
Trees, graphs, BFS/DFS
Dynamic programming (yes, the scary one)
Sorting, searching, bit manipulation
System design basics

Each day has a lesson page with explanations and then links to practice problems. Nothing groundbreaking in terms of content - it's more about the structure and pacing. You're not drowning in choices.

The tech stack (for the curious)

Built this as a side project over a few weeks:

Backend: Python/FastAPI running as ASGI on Vercel
Database: Cloudflare D1 (SQLite at the edge, surprisingly good)
Auth: Supabase for Google OAuth + email/password
Frontend: Server-rendered HTML with Jinja2 templates, vanilla CSS
Hosting: Vercel (free tier)

Yeah I know, no React. Fight me. For a content-heavy site like this, server-rendered HTML is honestly perfect. Pages load fast, SEO works out of the box, and I didn't have to wrestle with hydration bugs at 2am.

The D1 + Supabase combo is interesting. Supabase handles auth really well but I wanted edge-cached reads for the curriculum content, so D1 made sense there. Wouldn't do this for everything but for read-heavy content it's pretty solid.

What I learned building this

Scope creep is real. I originally wanted gamification, streaks, a community forum... stripped all of that. The MVP is just lessons + progress tracking and honestly that's enough for now.
SEO matters more than I thought. Spent a decent amount of time on meta tags, structured data, sitemap, the whole thing. Turns out Google actually indexes you faster if you do this stuff right. Who knew.
FastAPI on Vercel actually works. Was skeptical but the ASGI adapter handles it fine. Cold starts are noticeable but acceptable.
Simple UIs can still look good. No component library, just some CSS custom properties and a dark theme. Keeping it minimal actually made the design process way easier.

Why free?

Because I built it for myself first. I'm using it to prep for my own interviews. Figured other people might find it useful too. Maybe I'll add premium stuff later but for now everything is free, no paywalls, no "sign up to see the answer" nonsense.

Try it out

Check it out at crackcode.dev and let me know what you think. I'm genuinely looking for feedback - what topics are missing, what's confusing, what sucks.

Also just launched on Product Hunt today if you wanna show some support there.

If you're prepping for interviews right now, hope this helps. And if you've already landed your dream job... well, bookmark it for next time. We all know how this industry works lol.

Building in public @ iodevz.com