16 Problems • 37 Lessons • Java
By an engineer who has worked atApple&Amazon& more — cleared & conducted 50+ interviews
Crack Machine Coding Interviews with
Production-Grade Java
Complete, working Java implementations for LLD / Machine Coding rounds. Not pseudocode. Not theory. Real code you can run.
⚡Concurrency built-in from day one🎯Designed for 1–2 hour coding rounds🧩Step-by-step design → code walkthrough
💻
16
Problems
📖
37
Lessons
⚡
100%
Concurrent
🚫
0
Pseudocode
Why This Exists
Most LLD / Machine Coding Resources Waste Your Time
You've seen the pattern: 40 minutes of theory, 5 minutes of half-finished code, zero concurrency. Here's what's different.
📺YouTube Tutorials
- Incomplete implementations
- Skip concurrency entirely
- No design rationale
📚Theory Courses
- All diagrams, no code
- Never tested in interviews
- Missing practical trade-offs
🐙GitHub Repos
- No explanation or walkthrough
- Spaghetti code, no structure
- Impossible to learn from
✓
This Course Instead
Every problem comes with all of this
Complete working Java code
Thread-safe from the start
UML class diagram
Step-by-step walkthrough
What You'll Learn
Four Skills That Win Interviews
Each problem teaches all four. Not as separate chapters — as one integrated workflow.
Machine Coding Thinking
Break any problem into entities, relationships, and behaviors. Think like an interviewer evaluates.
Low-Level Design
Design class hierarchies, pick patterns, define interfaces. OOP + SOLID applied to real systems.
Concurrency Handling
Locks, semaphores, thread pools, atomic operations. Not an afterthought — integrated into every design.
Clean, Minimal Code
Single-file solutions. No framework bloat, no enterprise boilerplate. Just the design + logic.
Curriculum
Beginner to Advanced, Everything Included
Three progressive tiers — each building on the last. Browse every problem and lesson below.
Course Structure
BeginnerIntermediateAdvanced
🟢Beginner3 problems
Problems
Tic-Tac-ToeSnakes & LaddersVersion Manager
Key Concepts
Strategy PatternState MachinePrecomputation
🟡Intermediate6 problems
Problems
Elevator SystemLRU/LFU CacheBookMyShowParking LotVehicle RentalAmazon Locker
Key Concepts
SCAN AlgorithmSemaphoreThread ConfinementInterval Tree
🔴Advanced7 problems
Problems
Job SchedulerRate LimiterMessage QueueDependency BuilderTwitter FeedSnowflake IDCab Booking
Key Concepts
PriorityQueue + ConditionToken BucketPub-SubTopological Sort
📖
+ 37 In-Depth Lessons in the Learning Notebook
Every key concept above — Strategy Pattern, SCAN Algorithm, Token Bucket, Pub-Sub, and more — is explained step-by-step in the Learning Notebook with code examples, diagrams, and intuition. Problems and lessons are tightly cross-linked.
Full Table of Contents
💻
Machine Coding Problems
16 problems • Beginner → Advanced
🟡Intermediate LLD6
4Elevator System Design⚡ Concurrent5Cache Design (LRU + LFU)⚡ Concurrent6BookMyShow — Ticket Booking⚡ Concurrent7Vehicle Rental System8Parking Lot System⚡ Concurrent9Amazon Locker System⚡ Concurrent🔴Advanced Machine Coding7
10Job Scheduler Design⚡ Concurrent11API Rate Limiter (Token Bucket)⚡ Concurrent12Message Queue (Kafka-like)⚡ Concurrent13Dependency Builder⚡ ConcurrentFree14Twitter Feed Design⚡ Concurrent15Distributed ID Generator (Snowflake)⚡ Concurrent16Cab Booking System (Uber/Ola)⚡ Concurrent📖
Learning Notebook
37 lessons • 6 chapters • Deep dives into every key concept
🧱OOP Fundamentals8
1Classes & Objects: Blueprints and Buildings2Encapsulation: Protecting Your Data3Inheritance: Standing on the Shoulders of Giants4Polymorphism: One Interface, Many Forms5Abstraction: Hiding the Complexity6Interfaces: The Contract7Composition Over Inheritance: Has-A vs Is-A8Putting It All Together: A Mini Design Exercise📐SOLID Principles5
1Single Responsibility Principle (SRP)2Open/Closed Principle (OCP)3Liskov Substitution Principle (LSP)4Interface Segregation Principle (ISP)5Dependency Inversion Principle (DIP)🏗️Design Patterns6
1Strategy Pattern2Factory Pattern3Singleton Pattern4State Pattern5Observer Pattern6Command Pattern⚡Algorithms & Data Structures5
1Sum-Array Win Detection2DP Precomputation & Lookup Tables3SCAN (Elevator) Algorithm4Interval Trees & Overlap Detection5Topological Sort (Kahn's Algorithm)🔄Concurrency Deep Dive8
1Immutability: The Simplest Thread Safety2Thread Confinement: No Sharing, No Problems3Atomic Operations & CAS: Lock-Free Magic4Semaphores: The Bouncer at the Club5ReentrantLock & Condition: Advanced Wait/NotifyFree6ConcurrentSkipListMap: Thread-Safe Sorted Map7Hash-Based Executor: Per-Key Ordering8CompletableFuture: Async Without the PainConcepts ↔ Problems
Every design pattern, concurrency primitive, and algorithm used in the problems is explained in depth in the Learning Notebook. The two are tightly linked — concepts link to problems, and problems link back to concepts.
⚠️
Prerequisite
Basic Java knowledge is required — classes, interfaces, inheritance, and collections (List, Map, Set). No frameworks or build tools needed. Every solution is a single runnable Java file.
The Difference
Built for How Interviews Actually Work
📄
Single-File, Interview-Ready
Every solution is one Java file. Copy, paste, run. No multi-module setup, no build system needed.
🔒
Concurrency Is Not Optional
Locks, thread pools, atomic operations — woven into every design. Because interviewers expect it.
🔍
Step-by-Step Walkthrough
Every problem has an execution trace. See exactly what happens at each millisecond, in what order.
⚖️
Alternatives Considered
Every design decision is compared: what else was possible, why this approach won, what the trade-offs are.
🎯 Interview ReadyDesigned for 1–2 Hour
Designed for 1–2 Hour
Machine Coding Rounds
Every problem mirrors real interview constraints: limited time, clear requirements, expectation of working code. You practice exactly what you'll face.
Solve in the same time pressure as interviews
Code compiles and runs — not just compiles
Concurrency is always part of the evaluation
Common Mistakes This Course Prevents
1Starting to code without identifying entities first
2Ignoring concurrency until the interviewer asks
3Over-engineering with unnecessary patterns
4No clear separation of concerns
5Missing edge cases in booking/allocation systems
About the Instructor
Content carefully designed by an engineer who has worked at 3+ top product companies
This isn't a course written from Stack Overflow and YouTube. Every problem, every design decision, every concurrency trade-off in here comes from real experience building production systems at top-tier product companies — and from sitting on both sides of the interview table.
As an interviewee, cleared LLD rounds at top product companies. As an interviewer, evaluated dozens of candidates — and seen exactly what separates a passing solution from a failing one. That dual perspective is baked into every problem here.
50+Interviews
Cleared & Conducted
3+Top-tier
Product Companies
7+Years of
Production Java
Industry Experience
Apple
Software Engineer
Amazon
Software Development Engineer
Both sides of the table — as a candidate who cleared these rounds, and as an interviewer who evaluated others. That's the lens this course is built through.
How You Learn
Problem → Design → Code → Understanding
Every problem follows the same rigorous 5-step workflow. Here's what it looks like.
📋
Step 1
Understand Requirements
Design a Job Scheduler that executes tasks at specified times. Support ONCE, FIXED_RATE, and FIXED_DELAY modes. Must handle concurrent submissions.
Clear problem statement with constraints, clarifications, and expected behavior.
Pricing
One Payment. Lifetime Access.
No subscription. No drip-feeding. Everything unlocked — all 16 problems, all 37 lessons, every future update.
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- 1 free learning notebook lesson
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16 problems. 37 lessons. Every line of code explained. Your next machine coding interview won't catch you off guard.
LLD Machine Coding Course • Java • Interview Preparation
Built by engineers, for engineers