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New · System Design Refreshers are live

Interview-ready,
from days out to the night before.

Bite-sized refresher videos to re-up concepts fast. A large question bank with answers to drill, practice mode to let you practice with AI-grading, plus cheatsheets for the bits that slip. When something won't click, re-explain rewrites the answer simpler or deeper - and popular questions carry an interactive diagram to step through, free to view - or request one where it's missing.

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01 · Refreshers

Just enough. Just in time.

Short videos, one concept at a time - for a quick re-up. Ideal when you want a 101 on a concept or a quick refresh. Ideal for last-minute prep the night before an interview, when you need to grasp the concept quickly without diving into every detail.

Now live · 9 videos
Coming next Database Design Distributed Systems Frontend Performance Auth & Identity Roadmap
02 · Browse

Start where you actually work.

A large question bank spanning frontend, backend, infra, data and AI - curated and organised so you find yours in seconds.

ME MEAN 5 topics ME MERN 5 topics LA LAMP 5 topics DJ Django 6 topics RO Ruby on Rails 5 topics JA JAM 6 topics SO Serverless on AWS 5 topics FM Flutter Mobile 5 topics SB Spring Boot 7 topics NE .NET 6 topics VU Vue 5 topics GB Go Backend 6 topics FA FastAPI 6 topics RN React Native 5 topics IN iOS Native 5 topics AN Android Native 5 topics WE Web3 / Ethereum 6 topics DP DevOps / Platform 6 topics AE AI Engineer 6 topics AP AI-Powered Developer 4 topics CS Core SWE Interview Prep 12 topics
FD Frontend Development 20 topics BD Backend Development 26 topics DT Database Technologies 17 topics MD Mobile Development 11 topics SD System Design Concepts 20 topics TE Testing 16 topics DE DevOps 20 topics SA System Administration 23 topics SE Security 12 topics BT Blockchain Technologies 22 topics
03 · What's inside

A full toolkit. One job: getting you hired.

Refreshers for concepts that need quick re-up, interview questions organized by topic and difficulty, practice to test your knowledge, and cheatsheets you can absorb in minutes. And we're growing with new content. See what's shipping below.

01

Refreshers

Short videos, one concept at a time - for a quick re-up. Ideal when you want a 101 on a concept or a quick refresh. Scrub, revise, move on.

02

Interview Qs

Large question bank across different topics, ordered by difficulty - practice with commonly asked questions, expand to see the answer - simplify, go deeper, or visualize it as a diagram.

03

Practice

Attempt-first study mode. Answer each question yourself, then reveal it or AI-grade what you wrote - and mark it knew it, shaky, or didn't know. Per-topic mastery and a review queue track what to revisit.

04

Cheatsheets

Very concise references for different topics. Syntax, patterns, gotchas - sectioned and searchable, with the full library unlocked on Pro.

05 Coming soon

Deep Dives

Long-form videos/guides that build a topic from the ground up - concepts, trade-offs, examples. For when the interview is weeks away and you want real depth.

04 · See a real answer

The answer. Not a blog post.

Every answer is written to be said out loud - short enough to remember, structured to hit what interviewers listen for. This one's pulled live from the bank. Judge for yourself.

04 Explain the core components of Kafka architecture. Beginner

Kafka architecture consists of several key components:

  • Producer: Applications that publish (write) events to Kafka topics
  • Consumer: Applications that subscribe to (read) events from topics
  • Broker: Kafka servers that store data and serve client requests
  • Topic: Categories or feed names to which records are published
  • Partition: Sub-divisions of topics for parallelism and scalability
  • Zookeeper: Coordinates and manages Kafka cluster metadata (being replaced by KRaft)
Browse 6,600+ more answers
Practice

Don't just read answers - practice them.

Flip any topic into Practice mode: answer each question yourself first - out loud or typed - then reveal it, or let AI grade what you wrote. Mark how it went and your mastery builds as you go, so you always know what to review next.

  • Answer first - out loud or typed - then reveal
  • Self-grade: knew it, shaky, or didn't know
  • AI-grade your typed answer for instant feedback
  • Per-topic mastery bars show where you stand
  • A cross-topic review queue surfaces what to revisit
Start practicing See your mastery →
Re-explain

Get the answer your way.

Stuck on the answer, or want to push past it? Re-explain rewrites it on demand - simpler and from first principles, or deeper with the trade-offs and follow-ups an interviewer probes. And when words aren't enough, popular questions carry an interactive diagram - step through the code, watch the call stack, see what points where. Missing on the one you're reading? Request it free. The text modes live on every cheatsheet section too.

  • Simpler, deeper, or a diagram - one click
  • Interactive diagrams on popular questions - or request one free
  • Plain English, easy to follow
  • A clear way to say it in the interview
  • On questions and every cheatsheet section
Re-explain
Question

Explain the Virtual DOM and how it works in React.

Think of it like a rough draft. React keeps a lightweight copy of the page. When something changes, it compares the new copy to the old one, finds just the differences, and updates only the parts that changed - instead of redrawing everything.
Tailored for you · also on cheatsheets
187
Topics
6,600+
Questions
9
Refreshers
175
Cheatsheets
05 · Roadmap

What we're shipping, openly.

No vaporware. Here's what's live, what's in motion, and what's on the horizon - so you know what to expect.

Live today

Questions, AI, Cheatsheets, Refreshers

  • 6,600+ interview questions across many stacks and topics
  • Re-explain simpler, deeper, or as an interactive diagram - one click
  • Cheatsheets for most of the topics
  • 9 refresher videos across 2 topics · 44 min
Building now

More refreshers

  • Database DesignIn production
  • Distributed SystemsQ4 2026
  • Frontend PerformanceQ4 2026
  • Auth & IdentityQ3 2026

Get notified as new topics land.

Get notified
Next up

Deep Dives

  • Long-form video + guide, built ground-up
  • Concepts, trade-offs, real examples
  • For when the interview's weeks out

Be first when the first one drops.

Get notified
06 · Pricing

All 6,600 questions. $10 a month.

Start free with questions in every topic, previews of cheatsheets, refreshers and some credits to try out AI features like re-explain and AI-grading - no card needed. Ready to go deeper? Upgrade to Pro for the full library, every cheatsheet, every refresher and a generous monthly AI allowance.

Pro
$10/mo
$6.67/mo
Less than an hour of interview coaching
  • All 6,600+ questions - the full library
  • Every cheatsheet
  • Every refresher video, current and future
  • 1,000 monthly AI credits - fresh takes on ~100 answers, cheatsheet explains, and AI answer grading
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Billed $80 once a year · Save $40.
Just browsing?
Free
$0 / forever
  • Free questions in nearly every topic
  • A starter set of free cheatsheets
  • Preview select refreshers
  • Interactive answer diagrams on free questions - viewable by anyone, no account needed
  • Free AI explanations on every free question, and free diagram requests - plus 100 credits for fresh takes, and AI grading
Start free, no card
07 · Get started

Your interview is next week.
Start with the first question.

Start free with questions in nearly every topic, starter cheatsheets, refreshers, and free AI explanations. Pro unlocks the full library, every cheatsheet, every refresher, and 1,000 monthly AI credits for fresh takes.

Get Pro or browse questions