Crack Machine Coding Interviews with
Production-Grade Code
Complete, working Java implementations for LLD / Machine Coding rounds. Not pseudocode. Not theory. Real code you can run.
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.
- Incomplete implementations
- Skip concurrency entirely
- No design rationale
- All diagrams, no code
- Never tested in interviews
- Missing practical trade-offs
- No explanation or walkthrough
- Spaghetti code, no structure
- Impossible to learn from
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.
Beginner to Advanced, Progressively
Each tier builds on the last. Start with OOP fundamentals, end with distributed systems.
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.
Problems & Lessons
Scroll through the complete list of machine coding problems and learning notebook lessons.
Machine Coding Problems
16 problems • Beginner → Advanced
Learning Notebook
37 lessons • 6 chapters • Deep dives into every key concept
Concepts ↔ 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 (classes, interfaces, collections) is required.
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.
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.
Problem → Design → Code → Understanding
Every problem follows the same rigorous 5-step workflow. Here's what it looks like.
Understand Requirements
Design a Job Scheduler that executes tasks at specified times. Support ONCE, FIXED_RATE, and FIXED_DELAY modes. Must handle concurrent submissions.
Stop Reading About LLD / Machine Coding.
Start Building.
16 problems. 37 lessons. Every line of code explained. Your next machine coding interview won't catch you off guard.