First Steps in System Design: Designing Backend Architectures That Stand Out in Interviews

Learn cache strategies for large-scale systems by building them yourself with Spring Boot. Understand and implement solutions for issues such as Cache Penetration, Cache Stampede, and Hot Keys.

Learn common components of global-scale services through popular papers, books, and articles.

It covers the essential core of computer science that remains unchanged in the AI era. You can prepare for system design interviews for employment or career transitions.

Silicon Valley Internship and 30 Big Tech System Design & Open Source Practical Contribution Completion Course that survives even in the AI era. All students who submit their missions can apply for an internship at a local AI startup in Palo Alto, USA, and will be granted an interview opportunity with a document screening waiver. This course involves designing and scaling 30 practical system designs based on Big Tech cases such as Netflix, Tesla, Meta, and Tinder. Finally, you will design your own service from architecture to DB to scaling, and complete your portfolio and resume by contributing to an actual operational open-source AI coding agent project (which has achieved 8.6K+ cumulative downloads).

Beyond how to write a resume, we will show you how to manage your career and succeed in interviews.

Developer interview taught directly by a senior software engineer who went through Naver and Amazon and is currently at Microsoft!! This lecture focuses on the "developer interview" rather than the "coding interview". When hiring a developer or, conversely, when changing jobs or seeking employment, the "coding interview" is never the only thing that determines success or failure. Through this lecture, I hope you will learn more about how to hire a developer or prepare for a change or seeking employment.

This course is a practical design lecture that organizes the logic of passing interviews based on actual evaluation criteria used by public institution interviewers, tailored to each career stage of applicants. For early-career applicants, it presents stability and growth potential rather than perfection, For experienced professionals, it provides a performance structure translated into organizational language rather than a mere list of experiences, For career changers, it offers answers to organizational concerns rather than explanations of reasons. It clearly identifies why evaluation points differ by stage even for the same question, and what reassures or concerns interviewers. The focus is on redesigning passing answers not as "techniques for speaking well" but as structures that eliminate the possibility of rejection. This is a career stage-specific passing design guide that directly reflects the decision-making flow of interviewers, enabling early-career, experienced, and transitioning applicants alike to establish strategies suited to their position.

An AI system that grades and reviews your code in 5 seconds - imagination becomes reality. This course is an all-in-one project that builds a **'GitHub PR Automatic Analysis and Grading Bot'** using Spring AI. When a student submits an assignment (Pull Request), the server detects it and AI analyzes the code changes (Diff). The grading results are then stored in the database, feedback is automatically posted as GitHub comments, and students can check their results on a dedicated dashboard. From backend to AI integration and frontend (Vaadin) - all with Java! This is the ultimate introductory guide for all developers who want to complete their own AI service from A to Z.

This course guides you to accurately understand essential programming concepts and theories that are often neglected in the rush of implementation. By learning similar, contrasting, and related concepts together, you will master multiple ideas at once. After completing this course, you will become a developer with a solid conceptual foundation.

A smooth-flowing guide to Express.js, from basics to real-world application! A backend journey to truly master everything from basic server concepts to completing a CRUD project through hands-on implementation.

Regardless of the field! This is a lecture that covers the core fundamentals that developers must know in practice in an easy + code-oriented way. I highly recommend this lecture to all junior developers and job seekers who want to grow.

You can learn about the core functions of MySQL and how to effectively use them in your work. You can also gain a new understanding of important parts that you have been using for a long time and have overlooked, and gain in-depth database knowledge.

"Turn your Java code into the hands and feet of AI! Practical Agent Development with Kakao PlayMCP and Spring AI" Traditional LLMs are limited to answering based only on their trained data, which can lead to issues with recency and accuracy. In this course, you will learn **MCP (Model Context Protocol)**—the next-generation standard protocol for connecting AI with external tools. Using Spring AI, you will build a server that communicates with various platforms like Kakao PlayMCP through a single implementation. Master the entire process from theory to real-world deployment and platform registration through the 'Proverbs & Psalms Counseling Center (JAMSI)' project, and grow into a true AI agent developer who can empower AI to handle tools independently.

Kotlin Programming Language, which you can learn by practicing with 76 examples. You have to develop in Kotlin starting tomorrow, but you don't have time to study the grammar? Let's quickly learn all the grammar of Kotlin with the examples provided in this lecture.

This lecture covers how to easily implement game backend systems using UGS (Unity Gaming Service). You will practice essential features such as Guest and Username/Password authentication, game data storage, leaderboards, and Remote Config. UGS has built a perfect ecosystem with Unity, preparing a practical course for easy learning without entry barriers, allowing immediate application to your projects.

Have you ever thought about building a 'real system' beyond simply rendering screens? The real problem many developers commonly face is something else entirely. It's the limitation of a 'fake full-stack'—where things look plausible on the surface, but data synchronization frequently tangles, speed is frustrating, and you lose track of where to even start when just a few features are added. This isn't a problem that can be solved by simply memorizing one more Next.js feature. This course will resolve that frustration from the roots. Encyclopedia-style classes that just list features are boring, aren't they? Instead, we have tightly integrated the fundamental principles of Computer Science (CS) with the advanced architecture of Next.js. We will directly transplant into your fingertips the enterprise-level design skills required to flexibly withstand millions of visitors and maintain perfect data consistency.

Listening to the interview speech can help you pass the interview with flying colors.

You can learn about the core functions of MySQL and how to effectively use them in your work. You can also gain a new understanding of important parts that you have been using for a long time and have overlooked, and gain in-depth database knowledge.

This course was created to solve a common problem many people face while preparing for developer jobs: "I studied CS and data structures, but I get tongue-tied during interviews." While conducting actual interviews at companies like Naver, Kakao, and Toss, I noticed that most candidates have memorized concepts but cannot explain why those concepts are necessary or how they are applied in real-world situations. Rather than simple rote memorization, this course teaches you how to understand the interviewer's intent and provide more persuasive answers to the same questions. Whether it's the OSI 7 layers, data structures, or coding tests, we focus on why you need to know them, when they are used, and how to speak about them to receive a positive evaluation in an interview. This course is for those who want to become developers who can explain what they understand in their own words, rather than just giving the same answers as everyone else.

This course provides a step-by-step learning path, ranging from the fundamental usage of MySQL to advanced techniques required in real-world production environments. It covers a wide range of topics, including data modeling techniques based on various case studies and practical data, evaluating the effectiveness of Foreign Key designs, analyzing Google Calendar schema DDL, and modern DDL design principles. Through this course, you will gain an in-depth understanding of how to utilize MySQL as a core system component rather than just a simple database.