System Design Study Notes
HLD, scalability, networks, cloud architecture, and production systems.
FreeDesign Patterns Study Note PDF
A beginner-friendly Design Patterns PDF guide covering four important interview patterns: Factory, Singleton, Strategy, and Observer. This guide explains why design patterns exist, where each pattern is useful, how to implement them, and what trade-offs to discuss in interviews. It is designed for developers who already know basic OOP and want to understand reusable software design in a practical way. Topics Covered 1. Factory Pattern - Object creation logic, use cases, examples, pros, cons, and interview explanation. 2. Singleton Pattern - Single-instance design, logging/config examples, thread-safety concerns, and when to avoid it. 3. Strategy Pattern - Interchangeable algorithms, payment strategy examples, sorting/filtering behavior, and open/closed design. 4. Observer Pattern - Event subscription, notifications, pub-sub style behavior, and real-world examples. 5. Pattern Comparison - When to use each pattern and how to explain trade-offs clearly. What You Will Get 12-page detailed PDF guide Four important design patterns Code examples and real-life use cases Comparison tables Interview Q&A and revision notes Best For Software engineering students, backend developers, full-stack developers, Java/C#/C++/Python/TypeScript learners, LLD interview aspirants, and developers learning reusable software design.
FreeSystem Design Topics Interview Guide
A beginner-friendly System Design PDF guide covering 5 important interview topics: Rate Limiter, Notification System, Payment System, Search Engine, and URL Shortener. Perfect for students, developers, and tech interview aspirants who want to understand High-Level Design in a practical way. Prepare for system design interviews with this detailed and easy-to-understand PDF guide. This resource explains 5 commonly asked HLD interview topics in a structured way, with concepts, architecture flow, key components, trade-offs, and interview-style explanation. This PDF is designed for beginner to intermediate developers who want to build a strong foundation in backend system design without getting overwhelmed by complex theory. Inside this guide, you will learn how real-world systems are designed for scalability, reliability, performance, and fault tolerance. Topics Covered: 1. Design a Rate Limiter Learn API protection, throttling, Redis counters, sliding window, token bucket, user-based limits, and abuse prevention. 2. Design a Notification System Understand fanout strategies, message queues, retry handling, user preferences, multi-channel delivery, idempotency, and analytics. 3. Design a Payment System Learn secure transactions, payment flow, idempotency, database consistency, third-party integrations, failure handling, fraud prevention, and reconciliation. 4. Design a Search Engine Understand crawling, indexing, tokenization, inverted index, ranking, caching, sharding, and search performance. 5. Design a URL Shortener Learn short code generation, redirect flow, database design, caching, analytics, high availability, and scalability. What You Will Get: 27-page detailed PDF guide Interview-focused explanations Beginner-friendly language High-level architecture breakdowns Real-world backend system examples Key components and design trade-offs Saveable notes for revision Best For: Software engineering students Backend developers Full-stack developers Tech interview aspirants Developers preparing for HLD rounds Anyone learning system design from scratch