Whetstone — AI-graded interview prep

The problem

Re-reading flashcards isn't practice.

You can recognize the right answer when you see it — and still freeze when you have to produce it cold, out loud, under pressure. Most prep tools test your memory. None of them tell you whether what you'd actually say would survive an interviewer.

Re-reading notesNodding at model answers"I basically know this"→ Saying it out loud & getting graded

How it works

Three steps. Real practice.

No passive review. You produce the answer first — then the AI tells you how it actually held up.

STEP 01

Write your answer first.

Before you see the model answer, you type your own — the way you'd say it in the room.

STEP 02

Get graded by AI.

An AI scores your answer against a reference, point by point: what you covered, what you missed, what was weak.

STEP 03

Know exactly what to fix.

No vague "good job." Specific, actionable feedback on the gap between what you said and what a strong answer needs.

Why it's different

Built around what actually keeps you going.

Two things most prep tools miss: honest feedback and visible progress. Whetstone's AI grades your answers like an interviewer would — no vague "good job." And your progress is mapped as you practice, so you always see which topics you've mastered and which need work.

Honest, interviewer-grade feedback

Scored point-by-point against a reference — the gaps named, not glossed over.

Visible progress, mapped as you go

Seeing progress isn't just satisfying — it's one of the most reliable ways to stay motivated through long prep.

It's the difference between feeling ready and knowing you are.

Your mastery map

Live

DS
Algo
SQL
API
OOP
Sys
Net
DB
Caching
Sec
Async
Behav

Data structures

88%

System design

64%

Databases

22%

New Learning Strong Mastered

The science

Why writing your answer beats re-reading it

Producing an answer from memory — writing it, saying it — builds far stronger memory than reviewing it. It's called the testing effect, and it's one of the most replicated findings in learning science.

Whetstone is built on the two techniques researchers rate highest-utility — retrieval practice and spaced repetition. Most prep tools rely on the ones rated lowest: re-reading and highlighting. That's the difference.

Recall, one week laterDelayed test

80%

Practiced retrieval

Wrote the answer from memory

34%

Re-read notes

Studied it again, passively

In a landmark study, learners who recalled material retained 80% a week later. Those who just re-read it: 34%. Same material. More than double the retention.

Roediger & Karpicke, 2006 · Dunlosky et al., 2013

“

I'm a visual person. When I study, I need to see where I'm improvingand where I'm still weak — otherwise I lose motivation fast. Turns out that's not just me: it's called the progress principle— visible progress is one of the most reliable motivators in learning, because seeing how far you've come keeps you going when willpower runs out. Most interview prep tools ignore this. So I built Whetstone around it: your mastery mapped out as you practice, and AI that tells you honestly whether your answers actually land. I built the tool I needed.

Tina

Building in public

Early access

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Join the waitlist and help shape what gets built first. One quick question — it genuinely guides the roadmap.

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You know the answer. But would it actually pass the interview?

Design a URL shortener. Walk me through it.