Frontend System Design: Frontend as a Distributed System

You use Git every day, but are there still times when it scares you? When a `git push` is rejected, when a colleague says, "Please rebase and upload," or when that "detached HEAD state" message pops up. You’ve probably had at least one moment where your mind went blank, and you ended up deleting the entire folder just to clone it again. This course is for people like you. Julia Evans' 〈How Git Works〉, beloved by developers worldwide, is finally available in Korean. This isn't a course about memorizing commands. It’s a course where we take a slow, deep look at how Git actually works under the hood. What’s inside the `.git` folder, How branches are actually stored, Where "orphaned" commits go and how to recover them, And what "up to date with origin/main" actually means. It consists of 27 pages across 6 chapters: ★ Commits ★ Branches ★ Exploring the .git folder ★ Merging ★ Remote repositories ★ Surviving disasters Once you properly grasp the internal model, you'll be able to interpret any message Git throws at you on your own. Instead of memorizing commands, you'll start using it while understanding "why it works this way." I’ll share the promise Julia made on the first page of her zine: "Once you understand the internals, you can get yourself out of any Git mess."

This is an advanced frontend course designed for students and professionals with at least one year of web development experience. It is best suited for those with 2–3 years of industry experience who are facing a plateau in their skills or wish to learn about product architectures required by large-scale enterprises.

"JS Build System, still confused?" The JS Build System's concepts and practices that never quite clicked, unified!

The Next.js 15 App Router is a powerful architecture for building high-performance web services by perfectly controlling the boundary between server and client. This course clearly connects complex rendering mechanisms—from the operating principles of React Server Components (RSC) to the three major caching strategies (Static, Dynamic, and ISR)—through 12 practical missions. Through this, you will gain the ability to design file-system routing and nested layouts according to business requirements, completely breaking free from the anxiety of "vibe coding" where you copy code without understanding the principles. Ultimately, you will evolve into a Next.js architect who can instantly spot the blind spots in AI-generated code and proactively direct the optimal structure.

A must-take testing course if you want to become a competent frontend developer. Master testing from beginner to advanced all in one go 👊

In this course, you will learn how to create a chat application using React and Firebase.

If you feel lost about what to learn in an era where AI writes code, you can find clear answers in the principles of UNIX and the kernel—the unchanging essence of systems. Through a practical project that integrates Node.js with a C language engine (FFmpeg), this course delivers the perspective of the top 1% of architects who command entire systems without being swayed by technology trends.

This is mission content for a development project. We provide a PRD planning document, Figma designs, and API endpoints so that you can practice by implementing a timer app called DevTime yourself. Make the knowledge you have learned completely your own by implementing a project at a level similar to an actual service 🚀

Hashing, salting, JWT, symmetric and asymmetric keys, and even HTTPS and TLS. The backbone of security that we use every day yet always found vague and unsettling. If we have to face the countless neglected threats and technical debt someday, let’s properly tackle them once and for all this time.

This course goes beyond just using Express.js—you'll implement its internal engine from scratch to truly understand how real servers work. You'll gain hands-on experience growing as a server developer by building all of Express's components from the ground up, including routers, middleware, request-response objects, static file handling, and template rendering.

In the era of swift execution and validation, execute faster than anyone with VIBE Coding! Achieve complete monetization, from ads to payments, all by yourself.

A portfolio-focused course on deploying a React frontend and Spring Boot backend directly to the AWS cloud! This course is helpful for those who want to quickly deploy frontend and backend projects for their portfolio. You will gain the necessary knowledge for deployment through short-term, step-by-step practice, covering everything from server configuration to Docker, domain connection, Nginx, and HTTPS application!

In this course, you will learn the basics of how to use React and Node.

This is a lecture where you can learn JavaScript through theory and practice. We explain step by step so that even those who are new to coding can easily understand. Part 1 covers an overview of JavaScript, variables, data types, operators, control statements, and the basics of jQuery.

It covers machine learning concepts within the JavaScript environment. It covers the patterns and code for implementing machine learning with JavaScript and TensorFlow.js.

This is the most solid foundation course for beginners who want to learn JavaScript properly. This course will be the starting point for understanding the language called JavaScript, and you can perfectly prepare the basics to become a front-end (Vue, React, Angular) developer and server (Node.js) developer.

Through this lecture, students can create a web service similar to Instagram using HTML, CSS, and JS. (Only the front-end is implemented! The back-end server construction will be filmed in a later lecture.)

A course where you understand core JavaScript concepts and train to explain them verbally for interviews.

Document writing is the most challenging part for both aspiring and current developers! Create your own portfolio by looking at how successful candidates write their documents! We speak based only on documents that actually passed!

Beyond the basics of API design, CRUD implementation, and JWT authentication, all the way to backend architecture design! This is an introductory system design course to help you create 'your own backend architecture' so you can confidently discuss design experience in interviews.