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Practice exposes what you don’t know.

We make sure you learn it. Every design reveals the concepts you don’t have yet — review them on your schedule until they stick.

Built by an engineer who’s run this loop on themselves.

No spam — one email when we launch.See how evaluation works →

Every design, scored across four axes

  • Foundation
  • Structure
  • Depth
  • Delivery

The problem

As AI commoditizes coding, architecture judgment is the skill that compounds.

Books teach patterns. Shipping teaches judgment. This is the place to build judgment without waiting for the next staff-level project to hand it to you.

How it reads your design

Write your design. See the concepts you're still missing.

Each attempt returns the two concepts most likely to cost you next time. Those go into your review queue.

Your design

Rate limiter · 1M req/s
Level 1

Design a distributed rate limiter for an API gateway at 1M req/s. Cover the algorithm, where counters live, and how you handle hot keys.

Live evaluation

7 dimensions
Requirements clarity84%
Scale estimation62%
API design80%
High-level design70%
Bottleneck analysis36%
Scaling strategy60%
Trade-offs82%
Overall0%
From this evaluation

Review queue

The score is only useful if it turns into practice. Deltaframe queues the concepts that cost points, then brings them back before the next attempt.

AttemptReviewRe-attempt

Hot-key mitigation

Bottleneck analysis missed the write hotspot.

Review due

Today

Token bucket vs sliding window

Algorithm choice needs a clearer trade-off.

Next review

3 days

Two tracks, one loop

Coaching or Interview Prep.

Same practice loop, different pressure. Switch whenever your situation changes.

Coaching

Build the skill from the ground up.

Warmer feedback, explanations, and a review queue tuned to the concepts you keep missing. Progress measured over weeks, not one attempt.

Use when

Engineers building the skill from the ground up — or rebuilding it after years on adjacent stacks.

Interview Prep

Know where you stand before the interview does.

Strict scoring, time pressure, and an honest readout of where you stand. Only the gaps that still matter before the interview.

Use when

Engineers with an interview in days or weeks and limited prep time.

Questions

What people ask before they start.

Get notified when we launch

One email when the full practice product is live. No spam.