Technical screen
320 questionsOne coding problem, 45 minutes, live narration expected.
v3.0 — The Developer Learning Operating System
From code to Mastery.
Documentation, interactive labs, DSA playground, algorithm visualizers, MCQ rounds and company-specific interview prep — unified into one continuous system instead of scattered tabs.
- 650+
- Interview questions
- 150
- DSA problems
- 48k
- Monthly devs
1// twoSum.ts · O(n) Time · O(n) Space2export function twoSum(nums: number[], target: number) {3 const seen = new Map<number, number>();4 for (let i = 0; i < nums.length; i++) {5 const need = target - nums[i];6 if (seen.has(need)) return [seen.get(need)!, i];7 seen.set(nums[i], i);8 }9}$ ipd test twoSum.spec.ts 47/47 Passed · 41ms
THE PROBLEM · 00
Traditional learning is fragmented. We built the unified kernel.
Stop context-switching between docs, YouTube tabs and disjointed sandboxes. Everything a developer needs to learn, practice, prepare and grow lives in one continuous environment.
From the first line of a visualizer to the final mock interview, your progress is tracked inside a single persistent XP ecosystem.
UNIFIED KERNEL PIPELINE
Persistent XPdocs / javascript / control-flow
ReferenceSequential Control Flow
Read in-depth guides with inline runnable code, architecture diagrams & ⌘K search.
68% Guide Read · ⌘K Search0ms context switch
Continuous Kernel Active1 Persistent Identity →
01What we have
Fourteen surfaces. One operating system.
Every part of the platform hands off to the next one. Read a concept, practice it in a lab, watch it run, drill it in a quiz, then defend it in a mock interview round.
40+ guides
Documentation
Depth-first written guides, not video transcripts.
Reading is faster than watching when you already know 60% of a topic.
Explore surface
180 labs
Interactive Labs
A real editor and test suite inside every lesson.
Concepts stick when the suite goes green with your code.
Explore surface
150 problems
DSA Playground
Curated problems with hints, editorials and submissions.
Pattern coverage beats random problem grinding.
Explore surface
22 algorithms
Algorithm Visualizers
Frame-by-frame animation with the matching pseudocode line.
You cannot debug what you cannot picture.
Explore surface
650+ questions
Interview Preparation
Question banks per round: coding, design, behavioral.
Rehearsal removes the surprise from the real loop.
Explore surface
1,200 MCQs
MCQ Hub
Timed rapid-fire rounds with instant explanations.
Screening rounds are won on fundamentals under a clock.
Explore surface
6 tracks
Guided Roadmaps
Week-by-week plans that chain every surface together.
A finite path beats an infinite content library.
Explore surface
12 companies
Company Preparation
Banks tuned to how each company actually interviews.
Google's bar is not Stripe's bar.
Explore surface
live
Progress Tracking
Topic-level readiness, not a vanity completion bar.
Identify exact weaknesses before entering real loops.
Explore surface
8,420 avg
XP System
Every solved case, lab and quiz earns weighted XP.
Gamified retention backed by persistent telemetry.
Explore surface
12 days
Daily Streaks
One problem a day keeps the plan alive.
Daily momentum compounds over 18-week roadmaps.
Explore surface
02Documentation
Reference material written like a product, not a wiki
Explorer, folder tree, breadcrumbs, Mermaid diagrams, runnable snippets, tabbed examples and per-page progress. Everything is searchable with ⌘K and remembers where you left off.
docs / javascript / control-flow
docsjavascriptcontrol-flow
Sequential Control Flow
An await inside a loop serialises work on purpose. Reach for it when order matters — and for Promise.all when it doesn't.
1for (const task of queue) {2 await run(task); // sequential execution by design3}Mermaid Flowchart · Sequential ExecutionOrder Enforced
Queue [Tasks]
→await run(t1)
→t1 Complete
→await run(t2)
68% read
Covered tracks
14 TracksMaintained by senior staff engineers who interview candidates at top tech companies.
JavaScript
React
Angular
- Next.js
Node.js
Python
SQL
MongoDB
Git
- AI
- Prompt Eng.
- System Design
- HLD
- LLD
03Interactive programming labs
An editor that grades you, not a video that talks at you
Every lesson ends in a lab: a scoped file tree, a real editor, a test suite and an execution sandbox. You submit only when the suite is green — and the XP lands the moment it is.
lab / javascript / debounce
Active Lab:
+80 XP1// Lab 07 — debounce() implementation2export function debounce(fn, wait = 300) {3 let timerId;4 return (...args) => {5 clearTimeout(timerId);6 timerId = setTimeout(() => fn(...args), wait);7 };8} autosaved 13px fullscreen
Accepted+80 XP4/4 Suite Passed · 12ms
- fires once after quiet period3ms
- cancels pending calls4ms
- forwards latest arguments2ms
- preserves `this` binding3ms
Monaco Code Editor
Integrated VS Code engine with autocomplete, linting and real keybindings.
Console & Terminal Bar
Stream stdout, stderr, exception tracebacks and process exit codes.
DOM Live Preview
Interactive UI components render dynamically right beside your code.
Automated Test Runner
Visible & hidden test suites execute automatically on every save (⌘S).
Persistent Session Autosave
Code drafts survive browser refreshes, tab switching, and crash recovery.
Zen Mode & Custom Layouts
Toggle split view, font sizes and full-screen focus for distraction-free coding.
04DSA playground
150 problems, chosen for coverage — not volume
Filter by difficulty, company or pattern. Every problem ships with constraints, staged hints, an editorial, four language runtimes, submission history and a complexity report on each run.
playground / problems
| Problem | Level | Accepted | Companies |
|---|---|---|---|
Two Sum Array · Hash Map | Easy | 94.2% | Google · Amazon |
Longest Substring Without Repeat Sliding Window · String | Medium | 38.7% | Meta · Uber |
Course Schedule Graph · Topo Sort | Medium | 46.1% | Microsoft · Stripe |
Merge k Sorted Lists Heap · Linked List | Hard | 51.4% | Amazon · Netflix |
Word Ladder BFS · Graph | Hard | 37.9% | Google · Adobe |
3 staged hints 41ms runtime 44.2MB memory
Submission Heatmap
18 Weeks126 days of telemetry. Consistency compounds over time.
126 active days412 total submissions
68
Easy solved
54
Medium solved
19
Hard solved
Active Execution Console · Two Sum✓ 100% Accepted
> input: nums = [2,7,11,15], target = 9 > output: [0,1] > time: O(N) > space: O(N) ✓ Verified · 41ms · 44.2MB
05Algorithm visualizers
Watch the algorithm think, one frame at a time
Scrub, step, replay and race algorithms side by side. Every frame highlights the matching pseudocode line and the live state of your queue, stack or pointer window.
visualizer / merge-sort
Array Partition · Step 4/8O(N log N) Time
Partition [6..9]Comparisons: 36 · Swaps: 17
Graph ExecutionO(N) Space
queue → [E, F]
visited → {A, B, C, D}
depth → 2speed:1.6×
Pick an algorithm
22 AlgorithmsSelect an algorithm to watch real-time partitioning, comparisons, and memory pointer shifts.
Performance Insight
Compare algorithm time complexities to see why O(N log N) sorts beat O(N²) quadratic algorithms when dataset N reaches 10,000+.
06Interview preparation
Rehearse the whole loop, round by round
Filter by stack, difficulty and company. Each question ships with a model answer, the follow-up chain, a cheat sheet and a readiness score that updates as you rehearse.
prep / javascript / event-loop
Mediumasked at Google · Ubertechnical screen
Explain how the event loop schedules microtasks against macrotasks.
Core Evaluation Focus
Interviewers assess structured thinking, edge case awareness, and clear narration under pressure.
Readiness · JavaScript78%
System design
48 promptsHLD and LLD prompts with reference architectures and trade-off tables.
Behavioral
120 storiesSTAR-structured answers with the follow-ups interviewers actually ask.
Hiring manager
62 questionsScope, ownership and impact questions, mapped to each level.
Mock interviews run on a timer with an automated panel debrief.
07MCQ hub
Timed rounds that expose the gaps before a recruiter does
Sixty seconds a question. Instant explanation, XP on correct answers, a review-later queue for everything you fumbled, and a weekly leaderboard if you like the pressure.
mcq / javascript / round-4
Question 1 of 15
00:42When does the microtask queue get drained?
Explanation & Context
The queue is drained to empty after each macrotask completes and before the next render — which is why promise chains can starve timers.
review later · 2 queued+25 XP Earned
87%
Round accuracy · 13 of 15 correct
Weekly Leaderboard
Global Rank- 01 · sanjana.k4,820 XP
- 02 · you4,510 XP
- 03 · devraj4,190 XP
- 04 · m.okafor3,880 XP
08Guided learning roadmaps
A finite path, not an infinite library
Every track chains the same eight stops. Clear, structured guidance from your first lesson to final track mastery.
Track Overview
Frontend Architecture
12 weeks · 8 hrs/wk+2,400 XP
From semantic HTML and the event loop through React 19 concurrent patterns, performance budgets, WebGL rendering, and web accessibility.
Documentation
Stop 1 of 8Deep-first concept guides and interactive reference sheets.
02
Programming Labs
Stop 2 of 8Write code in a real Monaco editor with automated test suites.
03
DSA Playground
Stop 3 of 8Drill pattern-based algorithm problems until it becomes muscle memory.
04
Algorithm Visualizer
Stop 4 of 8Watch state changes frame-by-frame with matching pseudocode lines.
05
MCQ Rapid Rounds
Stop 5 of 8Prove recall under a 60-second timer before live interviews.
06
Interview Rehearsal
Stop 6 of 8Technical screens, system design loops, STAR stories & rubrics.
07
Production Project
Stop 7 of 8Ship a real application that withstands code review.
08
Track Mastery
Stop 8 of 8Verified track completion, ready to interview at top tech companies.
09Company preparation
Pick a company, get its entire interview shape
Not a logo wall. Select a company and the bank rewrites itself — its real problem set, the questions its panels ask, the design prompts it favours, your progress and the acceptance rate you're tracking against.
prep / companies / google
Hard bar182 problemsGraphs, DP, clean complexity narration
loop structure
5 rounds · 2 coding, 1 design, 1 behavioral, 1 googleyness
most asked problems
- Number of Islandsasked 41×Medium
- Word Ladder IIasked 28×Hard
- Longest Increasing Pathasked 22×Hard
- Meeting Rooms IIasked 19×Medium
difficulty · Hard
your progress116/182 problems
acceptance rate38%
- problems
- 182
- questions
- 94
- design
- 12
02The product
One workspace, on every desk you own
Not screenshots side by side — the real surfaces, layered the way they stack in use: the editor behind, the console, the tests and the reward floating over it.
documentation
Explorer, search, diagram, preview — one surface
Open a concept and the whole reading environment assembles: the tree on the left, command search over the top, the architecture diagram inline and an assistant that answers from the page you're on.
interviewprepdocs.dev/docs/react/reconciliation
preview · code
<ul>
{items.map(i => (
<Row key={i.id} {...i} />
))}
</ul>
tests · 4 / 4 passing
- ✓ empty inputpass
- ✓ single nodepass
- ✓ cycle detectedpass
- ✓ large graphpass
xp earned
+120
programming labs
Built for the late-night laptop session
Editor, console, tests, verdict and reward stack in one frame — the whole loop fits on a 13-inch screen without a single collapsed panel.
- 4
- language runtimes
- 41ms
- median run time
- 0
- context switches
- 100%
- keyboard driven
10Progress & XP
Momentum you can point at
XP, levels, streaks and goals exist for exactly one reason: to make the next session easier to start. Honest picture of readiness with real execution telemetry.
+340 this week
0
XP Earned · Level 7
Fire active
0 Days
Active Streak · Best 31
Top 5% rank
0
Badges Unlocked
1 session left
6 / 7
Weekly Goal Sessions
91-Day Learning Activity Heatmap
13 Weeks91 active sessionsCurrent track: "Graphs — Shortest Paths"
Skill Radar Graph
- JavaScript86%
- React74%
- Node.js62%
- DSA & Algorithms58%
- System Design41%
11Community & achievements
Nobody clears a loop alone
Discussion threads on every problem, peer solution reviews, weekly cohort rounds and verifiable certificates when a track is finished.
🌌 Unlocked
Graph Whisperer
Solved every graph problem in the core curriculum.
🔥 Unlocked
Thirty Days Streak
A full month without breaking daily learning goals.
📖 Unlocked
Editorial Mastery
Read official staff editorials after 50 accepted runs.
⚡In Progress
Mock Loop Ready
Cleared five timed mock interview panels with green scores.
48,000 active developers
Reading, solving, and reviewing code every month.
12,400 discussion threads
Alternative solutions, edge-case debates, and follow-ups.
Comprehensive curriculum
Docs and problem sets continuously refined for interview prep.
16Questions
Interview prep, answered
The things engineers ask before they start — what the platform covers, how to sequence your preparation, and what actually shows up in interviews.
What is Interview Prep Buddy?
Interview Prep Buddy is a free, all-in-one technical interview preparation platform for software engineers. It combines DSA pattern cheatsheets, interactive algorithm visualizers, browser-based coding labs, 1400+ interview questions, MCQ practice rounds, and system design guides — so you prepare in one place instead of across a dozen scattered tabs.
How do I prepare for a coding interview?
Work in four passes. First, learn the 16 core DSA patterns (two pointers, sliding window, binary search, BFS/DFS, dynamic programming, backtracking) rather than memorising individual problems. Second, drill problems by pattern until you can recognise which one a new question needs. Third, study system design fundamentals — caching, sharding, queues, consistency trade-offs. Fourth, review language-specific questions for your stack and rehearse behavioural answers with the STAR method.
Are the algorithm visualizers free?
Yes. Every algorithm visualizer on Interview Prep Buddy is free and needs no sign-up or payment. That covers sorting, searching, arrays, linked lists, stacks, queues, hash tables, heaps, trees, graphs, recursion, backtracking, dynamic programming, two pointers, and sliding window — each with step-by-step animations, synchronized pseudocode highlighting, and Big-O complexity panels.
Which DSA topics should I focus on for FAANG interviews?
Arrays and strings, hash maps, two pointers, sliding window, binary search, trees and binary search trees, graphs (BFS, DFS, topological sort), heaps, and dynamic programming account for the large majority of questions at Google, Amazon, Meta, Microsoft, and Apple. Recursion and backtracking appear regularly at the harder end. Bit manipulation and tries show up less often but are worth a pass before onsites.
How long does it take to prepare for a technical interview?
With consistent daily practice, most engineers need roughly 8 to 12 weeks: about 4 weeks to cover the core DSA patterns, 4 weeks of mixed problem drilling under time pressure, and 2 to 4 weeks on system design and behavioural rounds. If you already write code professionally and just need a refresher, a focused 4 to 6 week pass on patterns and mock problems is usually enough.
What is the difference between HLD and LLD interviews?
High-level design (HLD) asks you to architect a whole system — choosing databases, caches, queues, and service boundaries, then reasoning about scale, availability, and consistency trade-offs. Low-level design (LLD) narrows to one component and tests object-oriented modelling: classes, interfaces, relationships, and design patterns. HLD rounds reward breadth and trade-off reasoning; LLD rounds reward clean, extensible class design.
12 · Code to Mastery
This is not another video platform.
It's an entire developer operating system. Free to start — no credit card, no drip-fed course emails. Just the real docs, Monaco labs, algorithm visualizers, and the loop.
✓ Instant Access✓ No Credit Card Needed✓ 150+ Interactive Problems