Machine Coding Sheet
MaCo 30
Core 30 machine-coding problems — highest ROI for interviews.
Overall progress
0/30 solved
0%
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easy0/4
medium0/11
hard0/15
0/30
Solved
Utility
0/3 solved
| Status | Star | Problem | Difficulty | Key Focus | Notes |
|---|---|---|---|---|---|
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) |
Games
0/3 solved
| Status | Star | Problem | Difficulty | Key Focus | Notes |
|---|---|---|---|---|---|
Snake & Ladder Asked by:AmazonFlipkartMicrosoft+1 more | Easy | Entity Modeling, Game Loop | |||
Tic-Tac-Toe Asked by:GoogleMicrosoftAmazon+1 more | Easy | Scalable N×N Board & Win Strategies | |||
Chess Game Asked by:AmazonMicrosoftRiot Games | Hard | Validator Strategy & Command Move Reversal |
Infrastructure
0/8 solved
| Status | Star | Problem | Difficulty | Key Focus | Notes |
|---|---|---|---|---|---|
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 | |||
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 |
Fintech
0/4 solved
| Status | Star | Problem | Difficulty | Key Focus | Notes |
|---|---|---|---|---|---|
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 |
Commerce
0/3 solved
| Status | Star | Problem | Difficulty | Key Focus | Notes |
|---|---|---|---|---|---|
Hotel Booking System Asked by:Booking.comAirbnbExpedia | Medium | Strategy Refund & Fine-Grained Concurrent Booking | |||
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 |
Real-time
0/1 solved
| Status | Star | Problem | Difficulty | Key Focus | Notes |
|---|---|---|---|---|---|
Cricbuzz Scoreboard Asked by:YahooPaytmHotstar | Medium | Observer Pattern, Strategy Pattern, Thread Safety |
Marketplace
0/1 solved
| Status | Star | Problem | Difficulty | Key Focus | Notes |
|---|---|---|---|---|---|
Food Delivery (Zomato-lite) Asked by:DoorDashUberSwiggy+1 more | Hard | Strategy Pattern, Observer Pattern, Thread-Safe Resource Acquisition, State Transition Guards |
Productivity
0/2 solved
| Status | Star | Problem | Difficulty | Key Focus | Notes |
|---|---|---|---|---|---|
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 |
Search
0/2 solved
| Status | Star | Problem | Difficulty | Key Focus | Notes |
|---|---|---|---|---|---|
Search Ranking (Learning to Rank) Asked by:GoogleMicrosoftAmazon+1 more | Hard | NDCG, Feature Engineering | |||
Search Engine with Trie Asked by:GoogleMicrosoftYahoo | Hard | Trie suggestions, Inverted Index, TF-IDF Strategy, Boolean Query Intersections |
Geo
0/1 solved
| Status | Star | Problem | Difficulty | Key Focus | Notes |
|---|---|---|---|---|---|
Cab Sharing (Uber-lite) Asked by:UberLyftGrab+1 more | Hard | Strategy Pattern, Observer Pattern, Compare-And-Swap Concurrency, Geo Proximity |
Security
0/1 solved
| Status | Star | Problem | Difficulty | Key Focus | Notes |
|---|---|---|---|---|---|
Auth Service (OAuth / SSO) Asked by:OktaMicrosoftAuth0+1 more | Hard | Token Rotation, RBAC/ABAC |
DevOps
0/1 solved
| Status | Star | Problem | Difficulty | Key Focus | Notes |
|---|---|---|---|---|---|
Log Search (ELK-style) Asked by:SplunkElasticDatadog | Hard | Index Rotation, Hot-Warm |