Real-world architecture

Case studies built for deep reading

These long-form breakdowns now use a consistent framework with requirements, APIs, HLD, LLD, scaling challenges, trade-offs, visual sections, and takeaways.

Gemini CLI Lesson 8: Monorepo Modernization Case Study

Decomposing and modernizing legacy structures within a massive commerce monorepo is one of the most high-risk tasks a platform team can face. In a repository comprising hundreds of services and shared dependencies, a sin…

May 20, 202612 min read

Case StudyGemini CLI Mastery

#ai-ml#system-design#devops

Claude Code in Production: Migrating a Legacy Java Monolith to Spring Boot 3 — A Real-World Case Study

At a 200-person SaaS company, the backend team faced a mandatory migration: their Java 8 Spring MVC monolith (comprising approximately 50,000 lines of code) needed to move to Spring Boot 3.2, Java 21, and Project Loom vi…

May 15, 202613 min read

Case StudyClaude Code Mastery

#ai-ml#java#devops

DatabasesAdvanced

MySQL Schema Design Case Study: Building a Scalable E-Commerce Database

Database schema design is architecture. Like all architectural decisions, it must be driven by the query patterns and access patterns you actually have—not the ones you imagine you might need. In this case study, we deco…

May 15, 202614 min read

Case StudyComplete MySQL Mastery Roadmap

#databases#sql#mysql

System DesignAdvanced

System Design: Designing a Distributed Message Queue (Kafka)

1. Core Requirements & Scale Constraints A distributed message queue is the central nervous system of modern microservice architectures, responsible for decoupling system components, buffering spikes, and streaming real-…

Apr 26, 202611 min read

Case StudyHLD & LLD Mastery Course

#messaging#caching#databases

System DesignAdvanced

Database Sharding Part 7: Case Study - Scaling Discord to Billions

Designing a messaging storage system capable of handling trillions of messages with sub-millisecond query latency is one of the most demanding challenges in modern data engineering. In a chat application like Discord, th…

Apr 20, 202616 min read

Case StudyDatabase Sharding Mastery

#databases#system-design

System DesignAdvanced

Distributed Transactions Part 7: Case Study - The Global Fintech Ledger

Designing a global financial ledger is one of the most demanding challenges in systems engineering. The core requirements of a ledger are simple but absolute: never lose money, never create money, and maintain a 100% aud…

Apr 20, 202617 min read

Case StudyDistributed Transactions Mastery

System DesignAdvanced

Multi-Region DR: Warm Standby vs Active-Active

When a primary cloud region experiences a complete blackout due to fiber cuts, power grid failures, or database corruption, typical high-availability setups confined to a single geographic area become ineffective. Surviv…

Apr 20, 202618 min read

Case StudyReliability Engineering Mastery

#aws#system-design

System DesignAdvanced

System Design: Designing a Real-Time Ad Click Aggregator

Ad click aggregation represents one of the most high-throughput data engineering problems in modern advertising platforms. When billions of users click on ads across search engines, social media networks, and mobile appl…

Apr 20, 202619 min read

Case StudySystem Design Interview Mastery

#data-engineering#messaging#system-design

System DesignAdvanced

System Design: Designing a Collaborative Editor (Google Docs)

Designing a real-time collaborative document editor like Google Docs, Notion, or Figma represents one of the most complex challenges in distributed systems. When multiple users edit the same line of text simultaneously,…

Apr 20, 202623 min read

Case StudySystem Design Interview Mastery

System DesignAdvanced

System Design: Designing a Global Distributed Rate Limiter

Case Study: Designing a Global Distributed Rate Limiter Rate limiting is a critical operational safeguard for protecting distributed systems from abuse, intentional Denial of Service (DoS) attacks, brute-force exploits,…

Apr 20, 202612 min read

Case StudySystem Design Interview Mastery

#databases#security#system-design

System DesignAdvanced

System Design: Designing a Distributed Task Scheduler

1. Core Requirements & Scale Constraints A Distributed Task Scheduler is a foundational infrastructure component responsible for triggering operations at specific points in the future. Example use cases include schedulin…

Apr 20, 202613 min read

Case StudyBackend Systems Mastery

#messaging#system-design

System DesignAdvanced

System Design: Designing an E-commerce Checkout System

An e-commerce checkout and payment system is the financial engine of any retail platform. During flash sales or product drops, this system experiences massive write-concurrency spikes. Thousands of users attempt to purch…

Apr 20, 202619 min read

Case StudySystem Design Interview Mastery

#databases#system-design

System DesignAdvanced

System Design: Designing Google Maps (Navigation and ETA)

Designing a navigation system like Google Maps or Waze is one of the most intellectually challenging problems in software engineering. Calculate the optimal route between two points on opposite sides of a continent in le…

Apr 20, 202615 min read

Case StudySystem Design Interview Mastery

#geospatial#dsa#system-design

System DesignAdvanced

System Design: Designing Multi-Region Active-Active Shopping Carts

When building an e-commerce platform operating at a global scale, the shopping cart is one of the most business-critical systems. A single minute of shopping cart downtime directly translates to millions of dollars in lo…

Apr 20, 202615 min read

Case StudySystem Design Interview Mastery

#database#replication#system-design

System DesignAdvanced

System Design: Designing an Online Judge (LeetCode/HackerRank)

Designing a secure and scalable Online Judge (like LeetCode, HackerRank, or Codeforces) is one of the most high-risk systems engineering tasks. The core challenge lies in running untrusted, arbitrary user code on your in…

Apr 20, 202615 min read

Case StudySystem Design Interview Mastery

#security#orchestration#system-design

System DesignAdvanced

System Design: Designing a Global Payment Gateway (Stripe Scale)

Case Study: Designing a Global Payment Gateway (Stripe Scale) Designing a payment gateway (like Stripe, Adyen, or PayPal) is a unique engineering challenge. Unlike social platforms where eventual consistency is perfectly…

Apr 20, 202610 min read

Case StudyBackend Systems Mastery

#security#system-design

System DesignAdvanced

Project Case Study: Designing Stripe’s Ledger System

Recording transactions between millions of accounts is not a matter of simple arithmetic. In high-scale financial systems, a simple database update like UPDATE accounts SET balance = balance + amount is a dangerous anti-…

Apr 20, 202612 min read

Case StudySystem Design Interview Mastery

System DesignAdvanced

System Design: Designing Twitter (Timeline and News Feed)

Designing a real-time microblogging platform like Twitter (now X) is a flagship system design problem. The system must support massive read throughput, real-time message broadcasting, and rapid feed assembly under the co…

Apr 20, 202611 min read

Case StudySystem Design Interview Mastery

#databases#caching#scalability

System DesignAdvanced

Designing a High-Throughput Notification System for 100K Events per Second

Mental Model > Designing a high-throughput notification system capable of handling 100,000 events per second is primarily a high-volume data ingestion and fan-out stream routing problem. If a single upstream event (e.g.,…

May 10, 202512 min read

Case StudySystem Design Interview Mastery

#messaging#performance#system-design

DatabasesAdvanced

Designing a Database Sharding Strategy for 100 Million Users

Vertical scaling has a ceiling. For most high-transaction applications, that ceiling arrives somewhere between 1 million and 10 million users, depending on write patterns and data size. At 100 million users, the question…

Apr 14, 202513 min read

Case StudyBackend Systems Mastery

#databases#system-design