System Design Study Notes

Java Design Patterns

sagar saini@curiousdevlabs

Secure Dynamic Links Live Events Interview Guide

sagar saini@curiousdevlabs

Design a system that generates secure, dynamic access links for users who are entitled to watch live streaming content such as a cricket tournament. The design must survive the predictable traffic surge at match start, keep link generation fast, and reduce the usefulness of leaked or shared links. Best For Backend developers, full-stack developers, software engineering students, system design interview aspirants, and developers who want to move from basic backend knowledge to interview-ready architecture thinking.

Design Patterns Study Note PDF

sagar saini@curiousdevlabs

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.

System Design Topics Interview Guide

sagar saini@curiousdevlabs

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