Develow
A proof-of-work rating for AI-era engineers→

We make apps for real world problems

FSD skill rating for AI-native full stack developers. Made for the Hacker Rank, Code Signal, CoderPad AI assisted interviews

Get your rating — free→Download the IDE

Free to start · Mac · Windows · Linux

1760± 95
Product EngineerFSD Rating
Develow IDE — Shopping Cart I · Rated⏱ 12:40
cart.pystore.py
11·def apply_discount(self, code):
12· rule = self._lookup(code)
13· return self.total - rule.amount
14·
15·
16·
Failing8 / 12 tests passed

Powered by the latest models from

AnthropicAnthropic
OpenAIOpenAI

Always up to date with the frontier models from Anthropic and OpenAI.

Grounded in assessment research

.33

Work-sample validity ceiling (Roth 2005) — we claim no more than the science allows.

0.927

Elo↔IRT difficulty correlation across 50,055 attempts (EDM 2020).

2,294

Real repository issues behind the test-verified format (SWE-bench, ICLR 2024).

RCT

How you use AI drives skill retention — not whether you use it (Anthropic 2025).

One number, honestly reported

Your rating climbs as your uncertainty shrinks

Every rated challenge updates your FSD Rating against the problem's learned difficulty. The shaded band is your confidence interval — it tightens the more you prove.

12001400160018001760± 95Day 1Rated challenges completedDay 90

Illustrative trajectory. The shaded band is the ± rating deviation — it narrows as more rated challenges are completed.

Built for the AI era

Four dimensions the rating actually measures

AI changed software development. The engineers who thrive aren't the ones typing the most code — they're the ones who can direct AI and ship with confidence. The rating measures exactly that.

1

Understand systems

Read the problem and the codebase first — know the fundamentals well enough to navigate.

2

Direct AI effectively

Let AI do the heavy lifting while you point it at what actually matters.

3

Verify solutions

Run the tests and confirm the fix holds — because you know what correct looks like.

4

Ship with confidence

Submit production-ready work — and be able to explain exactly why it's right.

Not one skill

A full-stack fingerprint, not a single score

One scalar can't say "great at React, shaky on auth." The rating is multidimensional, so a weak layer shows — and the public number is penalized for being lopsided.

AI Orchestration1860Frontend1810Backend / API1740Testing1700Security / Auth1680Database1510

Sample profile

FSD 1760 ± 95

AI Orchestration1860 ± 100
Frontend1810 ± 90
Backend / API1740 ± 110
Testing1700 ± 120
Security / Auth1680 ± 130
Database1510 ± 160

Where you stand

See exactly where you rank

You
← lower ratedTop 18% of rated developershigher rated →

Sample rating 1760 → Product Engineer

Under the hood

How a submission becomes a rating

Grading is server-side against a hidden reference solution — you can't self-grade, and brute-forcing submissions decays their value.

Step 1

Graded 0–100

Your diff is judged against a hidden reference + rubric by the server-side grader.

Step 2

Continuous Elo

That score updates your rating against the problem's learned difficulty.

Step 3

± Uncertainty

A Glicko-2 confidence interval tightens as you complete more rated challenges.

Step 4

Skill vector

Only the skills a problem exercises move — weighted by its rubric.

Step 5

ML calibration

Offline models recalibrate difficulty and recommend your next challenge.

Learn freely, prove deliberately

Practice mode and Rated mode

Practice mode

Learn freely. Build the reps.

✓Unlimited attempts
✓Hints and AI fully encouraged
✓Reveal the reference solution anytime
✓Little to no rating impact

Rated mode

Prove it. This is what counts.

✓Time-boxed with hidden tests
✓Limited submissions — brute force decays
✓Server-side grading, no self-grading
✓Moves your FSD Rating and skill vector

Speed is key

A rating that proves you can crack the AI interview

Using the exact interview IDE and AI tools used at software companies, we compiled real-world problems asked by big tech — and turned your performance into a credible, shareable rating.

Browse the missions→
HackerRankHackerRank
CoderPadCoderPad
CodeSignalCodeSignal

Logos shown to reference the coding-interview formats we grew up on. Not affiliated with or endorsed by HackerRank, CoderPad, or CodeSignal.

Where speed meets maintainability

Download the free Develow IDE

Learn test-driven development with DVL AI — the methodology engineers use to ship 10x faster. Never get stuck again.

✓Investigate the codebase
✓Find the root cause
✓Generate a plan
✓Explain the architecture
✓Implement a solution
✓Teach you how it works

Real work, not exercises

Every rated challenge moves your number

Each mission is a real engineering job, scoped to a focused rep — across React, Node, Python, FastAPI, Go, Postgres and more.

Mission #12Feature

Add search to an online store

Start mission →
Mission #37Debugging

Fix a checkout failure

Start mission →
Mission #58Feature

Launch multi-language support

Start mission →
Mission #81Quality

Improve accessibility

Start mission →
Mission #114Performance

Scale for Black Friday traffic

Start mission →
Mission #142Feature

Ship a real-time notifications feed

Start mission →
Free question

Get a free Amazon question (2026)

A real Amazon full-stack debugging OA — MovieDB I. Drop your email and we'll send it over, free.

No spam. Unsubscribe anytime.

A clear path to product engineering

No tutorial hell. Just momentum.

  1. 1
    Month 1Day 1

    Build Products

    Learn how modern applications are structured and shipped. Get hands-on with frontend, backend, databases, and Docker through real, runnable projects.

  2. 2
    Month 2Day 30

    Ship Features

    Move beyond tutorials. Add functionality, fix bugs, and navigate real codebases — watching your FSD Rating climb with every rated challenge.

  3. 3
    Month 3Day 60

    Think Like An Engineer

    Work through realistic product challenges and AI-assisted workflows. Walk into any interview with a rating that proves you've already done the work.

0+
Real-world rated challenges
0
Product engineering families
0+
Top stacks — MERN, PERN, FastAPI, Go

Pricing

Upgrade for the full 90-day roadmap

Free

$0/ forever
  • ✓Download the Develow IDE
  • ✓Run sample problems
  • ✓Provisional FSD Rating
  • ×Full problem library
  • ×Full rated-mode scoring
Download free

Develow Pro

Most popular
$89.99/ year$119.99

That's 25% off — under $7.50/mo, billed yearly.

  • ✓The full 90-day product engineering roadmap
  • ✓Rated mode + full skill ratings
  • ✓Browse by company
  • ✓AI search across the catalog
  • ✓Everything in Free
Upgrade to Develow Pro →

Cancel anytime. Secure checkout via Stripe.

Built for every background

Frequently asked questions

Whether you come from software, design, business, or product — Develow is built to accelerate your learning rate. Speed is the whole point.

It's a single, honestly-reported number (with a ± confidence interval) that reflects how well you ship correct, verified changes in real codebases across the full stack. It starts provisional and sharpens as you complete rated challenges.

Yes. Missions start small and DVL Agent works right beside you — it can investigate the codebase, explain the architecture, and teach you how a fix works. You learn by shipping real software from day one instead of grinding abstract puzzles.

Absolutely. Designers already think in systems and user outcomes. Develow turns that instinct into shipped features — you'll learn just enough of the stack to build, with AI handling the boilerplate so you move fast.

Perfect fit. Product and business people who can direct AI to ship working software are the new force multipliers. Missions teach you to scope problems, build features, and verify they work — the core of Product Engineering.

Start building your rating today

Work through real-world problems with DVL Agent, earn your FSD Rating, and build the skills companies actually pay for.

Get your rating — free→Download the IDE