Machine Coding Sheet

MaCo 60

MaCo 30 plus extended coverage across all categories.

Overall progress

0/60 solved

0%


easy0/5

medium0/27

hard0/28

Utility

0/4 solved

StatusStarProblemDifficultyKey FocusNotes
Parking Lot
Asked by:AmazonGoogleMicrosoft+2 more
Easy

Inheritance, Enums, Strategy Pattern

Library Management System
Asked by:AmazonMicrosoftGoogle
Easy

Search & Strategy Penalty Logic

Vending Machine
Asked by:GoogleAmazonMicrosoft
Medium

State Pattern (Idle/Dispense)

Coffee Machine
Asked by:GoogleAmazonMicrosoft
Medium

Decorator Pattern, State Pattern, Inventory Checks, Thread-Safe Brewing

Games

0/4 solved

StatusStarProblemDifficultyKey FocusNotes
Snake & Ladder
Asked by:AmazonFlipkartMicrosoft+1 more
Easy

Entity Modeling, Game Loop

Tic-Tac-Toe
Asked by:GoogleMicrosoftAmazon+1 more
Easy

Scalable NxN Board & Win Strategies

Deck of Cards / Poker
Asked by:SonyMicrosoftZynga
Medium

Rule Engine, Hand Evaluation, Sorting, Kickers Tie-breaking

Chess Game
Asked by:AmazonMicrosoftRiot Games
Hard

Validator Strategy & Command Move Reversal

Infrastructure

0/18 solved

StatusStarProblemDifficultyKey FocusNotes
Elevator System
Asked by:GoogleAmazonMicrosoft+1 more
Medium

State, Strategy (Dispatching)

API Rate Limiter
Asked by:StripeGoogleAmazon+2 more
Medium

Token Bucket, Sliding Window

Logger Library
Asked by:GoogleAmazonSplunk+1 more
Medium

Strategy Formatter & Asynchronous Composite Sinks

Notification Service
Asked by:MetaAmazonApple+1 more
Medium

Factory Method, Strategy Pattern, Decorator Pattern, Rate Limiting

File System (Unix-like)
Asked by:MicrosoftAppleGoogle+1 more
Medium

Composite Pattern, Concurrent Read/Write Locks, Hierarchical Path Resolution

Distributed ID Generator
Asked by:TwitterMetaMicrosoft+1 more
Medium

Snowflake Strategy, Clock Providers, Resilient Clock-Skew Backoffs, Thread-Safe Bitwise Math

In-Memory Cache (LRU/LFU)
Asked by:RedisLabsAmazonTwitter+1 more
Medium

Strategy Pattern, Generics, Concurrent Read-Write Locks, Eviction Mechanics

A/B Testing Library
Asked by:NetflixMetaOptimizely+1 more
Medium

Hashing, User Bucketing

Basic Blockchain
Asked by:CoinbaseBinanceRipple
Medium

Hashing, Chain Validation

Airport Management System
Asked by:AmadeusSabreBoeing
Medium

Resource Allocation (Gates)

Unit Testing Framework
Asked by:JetBrainsMicrosoftGoogle
Medium

Reflection, Annotation Logic

In-Memory Key-Value Store
Asked by:RedisLabsGoogleAmazon+1 more
Hard

Nested Transactions & Command Logs

Git Version Control
Asked by:GitHubGitLabAtlassian+1 more
Hard

Composite Pattern, Hashing, Directed Acyclic Graph (DAG)

Pub-Sub System (Kafka-lite)
Asked by:LinkedInConfluentUber+1 more
Hard

Observer & Thread-safe Offset Streams

Job Scheduler
Asked by:GoogleAirbnbNetflix+1 more
Hard

Command & Observer Patterns, PriorityQueue, Exponential Backoff, Concurrent Locks

In-Memory SQL Database
Asked by:OracleMicrosoftAWS
Hard

Query Parser, Row Storage

Workflow Engine
Asked by:TemporalUberNetflix+1 more
Hard

DAG Execution, Callback

Package Manager
Asked by:npmGitHubMicrosoft+1 more
Hard

Dependency Graph Resolution

Fintech

0/7 solved

StatusStarProblemDifficultyKey FocusNotes
Expense Tracker
Asked by:RobinhoodBlockIntuit
Easy

Aggregation, Category Strategy

ATM Machine
Asked by:GoogleMicrosoftJPMorgan Chase
Medium

Chain of Responsibility & State Pattern

Splitwise
Asked by:UberMicrosoftFlipkart+1 more
Hard

Min-Cash Flow, Graph Modeling

Banking Ledger
Asked by:StripeBlockRevolut+1 more
Hard

Double-entry, Immutability

Digital Wallet
Asked by:PayPalBlockStripe+1 more
Hard

Command Pattern, Deadlock Prevention, Transaction Rollback, ACID

Stock Brokerage System
Asked by:RobinhoodCoinbaseGoldman Sachs
Hard

Command Pattern, Order Matching Engine, Priority Queues, Observer Pattern, Thread-Safe Order Books

Crypto Wallet
Asked by:CoinbaseBinanceLedger+1 more
Hard

Signing, Ledger Immutability

Commerce

0/5 solved

StatusStarProblemDifficultyKey FocusNotes
Hotel Booking System
Asked by:Booking.comAirbnbExpedia
Medium

Strategy Refund & Fine-Grained Concurrent Booking

Coupon Management System
Asked by:AmazonWalmartShopify
Medium

Rule Engine, Stacking Logic

Movie Booking (BookMyShow)
Asked by:AmazonFlipkartTicketmaster+1 more
Hard

Concurrency, Transactional Locks

Inventory Management
Asked by:AmazonWalmartShopify
Hard

Two-Phase Reservation, TTL Cleanup, Observer Pattern, Thread-Safe Inventory Decrements

Auction System
Asked by:eBayAlibabaSotheby's
Hard

Observer, High-freq Bidding

Real-time

0/1 solved

StatusStarProblemDifficultyKey FocusNotes
Cricbuzz Scoreboard
Asked by:YahooPaytmHotstar
Medium

Observer Pattern, Strategy Pattern, Thread Safety

Marketplace

0/2 solved

StatusStarProblemDifficultyKey FocusNotes
Car Rental System
Asked by:UberLyftHertz+1 more
Medium

Strategy Pattern, State Pattern, Concurrent Collections, Atomic Reference locks, Observer Notifications

Food Delivery (Zomato-lite)
Asked by:DoorDashUberSwiggy+1 more
Hard

Strategy Pattern, Observer Pattern, Thread-Safe Resource Acquisition, State Transition Guards

Productivity

0/3 solved

StatusStarProblemDifficultyKey FocusNotes
Meeting Scheduler
Asked by:MicrosoftGoogleUber+1 more
Medium

Concurrency, Interval Trees

Task Planner (Jira-lite)
Asked by:AtlassianMicrosoftSlack
Medium

State Pattern, Observer Pattern, Factory Method, Capacity Check

Survey Monkey (Survey System)
Asked by:QualtricsGoogleMicrosoft
Medium

Dynamic Form Modeling

Search

0/2 solved

Social

0/3 solved

StatusStarProblemDifficultyKey FocusNotes
Tinder Swipe Engine
Asked by:Match GroupTinderBumble
Medium

Matching Logic, Geo-filter

News Feed Ranker
Asked by:MetaByteDanceTwitter+1 more
Medium

Scoring Algorithms

LinkedIn (Social Graph)
Asked by:LinkedInMetaTwitter
Hard

Bidirectional BFS, Strategy Pattern, Observer Pattern, Graph Traversals, Concurrent Graph Nodes

Geo

0/2 solved

StatusStarProblemDifficultyKey FocusNotes
Cab Sharing (Uber-lite)
Asked by:UberLyftGrab+1 more
Hard

Strategy Pattern, Observer Pattern, Compare-And-Swap Concurrency, Geo Proximity

Ride Pooling Logic
Asked by:UberLyftGrab+1 more
Hard

Route Overlap Algorithms

Education

0/1 solved

StatusStarProblemDifficultyKey FocusNotes
Online Judge (LeetCode-lite)
Asked by:GoogleMicrosoftHackerRank
Hard

Sandbox Strategy, Observer Pattern, Thread-Safe Judge Pool, Leaderboard Aggregation

IoT

0/1 solved

StatusStarProblemDifficultyKey FocusNotes
Smart Home System
Asked by:AppleGoogleAmazon
Medium

Command & Composite Patterns, State Synchronization, Observer Registry, Bounded History Logs

Messaging

0/1 solved

StatusStarProblemDifficultyKey FocusNotes
Discord / Slack (Messaging)
Asked by:DiscordSlackMeta+1 more
Hard

Session Management, Pub-Sub

Resilience

0/1 solved

StatusStarProblemDifficultyKey FocusNotes
Circuit Breaker
Asked by:NetflixAWSGoogle+1 more
Medium

State Transitions (Open/Closed)

Ads

0/1 solved

StatusStarProblemDifficultyKey FocusNotes
Ad-Serving Engine
Asked by:GoogleTradeDeskMeta
Hard

Bid Selection, Auction Logic

Security

0/2 solved

StatusStarProblemDifficultyKey FocusNotes
Auth Service (OAuth / SSO)
Asked by:OktaMicrosoftAuth0+1 more
Hard

Token Rotation, RBAC/ABAC

Fraud Detection Rules Engine
Asked by:StripePayPalCoinbase+1 more
Hard

Predicate Logic, Thresholds

Media

0/1 solved

StatusStarProblemDifficultyKey FocusNotes
Podcast Player
Asked by:SpotifyAppleGoogle
Medium

State (Play/Pause), Playlists

DevOps

0/1 solved

StatusStarProblemDifficultyKey FocusNotes
Log Search (ELK-style)
Asked by:SplunkElasticDatadog
Hard

Index Rotation, Hot-Warm