Practical preparation for coding tests and interviews, directly taught by interviewers from Naver, Kakao, Line, Coupang, and Baemin.

This course goes beyond simple CRUD-level database usage to help you acquire PostgreSQL skills necessary for the AI era from a practical perspective. Based on AI development experience in Silicon Valley, you will learn step-by-step how to design and utilize JSON, indexes, transactions, and even pgvector in real-world services, while mastering methods to solve complex data structures and performance issues.

This course focuses on solving the problem of getting stuck in interviews and practical work due to a lack of understanding of why certain structures and configurations are necessary, rather than just teaching how to configure NGINX. Based on experience evaluating numerous candidates as an interviewer for companies like Naver, Kakao, and Toss, I explain how to describe and utilize NGINX from the perspectives of performance, scalability, and operations through hands-on practice. The core of this course is to help you develop a mindset capable of tracing traffic flow and troubleshooting problems, rather than just memorizing configuration values.

Build a scalable real-time event streaming order processing system using Spring Boot 3.x + Kotlin, establishing a Kafka cluster, and leveraging PostgreSQL CDC, Debezium Connect, and Apache Avro schemas.

This course is a master class that systematically covers the fundamental principles and practical applications of MongoDB. Starting with core MongoDB concepts, you will systematically learn essential topics for practical work, such as database design, CRUD operations, indexing, aggregation pipelines, performance optimization, transactions, and security. It explains topics step-by-step so even beginners can understand, and you can deeply learn the working principles of MongoDB through exercises and examples. This is the best introductory and practical course for developers who want to build strong MongoDB skills for practical work.

Develop a scalable real-time WebSocket chat server capable of handling high traffic by building a 3-instance cluster with Spring Boot 3.x and Kotlin, utilizing Redis Pub/Sub for distributed messaging and Nginx as a load balancer.

The biggest challenges in operating batch systems that process millions of records are performance degradation and the difficulty of recovery in the event of a failure. These issues cannot be solved with simple loops or poor design. Based on my experience of reliably processing large-scale data in real-world service environments, this course covers the structure and operating principles of Spring Batch and provides design methods to achieve both performance and stability. Moving beyond simple functional descriptions, this course will help you develop fundamental data processing problem-solving skills through batch architectures that can be applied immediately in practice.

You've probably experienced the frustration of using Redis without being able to explain why it was designed a certain way or why a particular pattern was adopted. Through my own hands-on experience and time as an interviewer, I have come to treat Redis not merely as a simple cache, but as a core component that dictates service stability and scalability. Rather than just memorizing commands, this course draws on my experience to explore how to choose the right architecture for real-world traffic environments and the associated trade-offs, empowering you to establish your own criteria and confidently explain your decisions in both interviews and on the job.

This course covers how to set up multi-module projects from scratch using Kotlin and Spring Boot. It proceeds with a hands-on approach, covering everything from the basic concepts of modularization to Gradle configuration, managing dependencies between modules, and actual application development. If you are a beginner or intermediate developer looking to learn the fundamentals and practical application of multi-modules, please refer to this course.

How will you handle exploding traffic? Learn how to build resilient and flexibly scalable architectures through practical EDA (Event-Driven Architecture) design patterns using Kafka, Spring, CDC, and Temporal. A Kakao developer shares real-world experience with clear, easy-to-follow explanations that even non-majors can understand. A practice-oriented course covering everything from real-time data flow and event processing to microservice integration!

This course is for developers who want to find fundamental solutions in environments where response times slow down as traffic increases, thread pools are quickly exhausted, and bottlenecks worsen with more external API calls. It helps you look at problems from the perspective of changing the architecture itself, rather than simply scaling out servers. Through this course, you will first understand the limitations of the traditional Spring MVC "Thread per Request" model. You will examine at the code level why throughput doesn't increase even when CPU resources are available, and exactly how blocking I/O occupies system resources. Next, you will learn the concepts and standard specifications of Reactive Streams and master how to handle data streams using Reactor's Mono and Flux. Beyond simple usage, you will learn through hands-on practice how data flows start, how they are consumed, and how throughput is controlled. In particular, you will directly implement design patterns that prevent OOM (Out of Memory) or overloads using Back Pressure. Additionally, you will understand the event loop-based processing structure of Spring WebFlux and conduct comparative exercises on how Non-Blocking I/O operates during actual request processing. By placing MVC and WebFlux side-by-side to verify their structural differences, you will also establish criteria for when to choose Reactive. This goes beyond simply "learning asynchrony." You will learn how to handle more requests with fewer threads, how to maintain a stable flow in environments with high external API dependencies, and develop the design intuition to secure throughput in high-concurrency environments.

Learn the SAGA transaction management technique for maintaining data consistency in distributed environments through a hands-on approach. You will configure three microservices using Spring Boot and Docker, and implement both Orchestration and Choreography patterns using Kafka and MySQL. Through this course, you will master core concepts applicable to real-world scenarios, including the operational principles of distributed transactions, designing compensating transactions, and handling fault recovery.

Learn how to design and handle large-scale data architectures that process hundreds of billions of records using only pure SQL and core MySQL features, alongside a Toss developer who handles hundreds of billions of financial traffic transactions and a developer who started as a non-major and is now developing platforms in Pangyo.

Learn the process of building essential Observability in a Microservices Architecture (MSA) environment from basics to practical application. Master standardized data collection using OpenTelemetry, trace storage and search through Grafana Tempo, and visualization using TraceQL through step-by-step hands-on practice. You can learn how to track service flows through distributed tracing, identify bottlenecks, and analyze the root causes of failures.

Systematically learn the distributed NoSQL database Cassandra, from foundational concepts to real-world applications. Build your large-scale data processing skills through hands-on practice and practical theory covering data modeling, query optimization, and cluster configuration. Even without prior database experience, you can become a Cassandra expert by learning from the practical know-how of a Silicon Valley developer.

When you find yourself constantly updating Swagger documentation, aligning API specs, and repeatedly communicating with the frontend, you start to wonder, "Why am I doing the same thing twice?" I also felt similar frustrations in my professional experience, which led me to use GraphQL extensively and develop an interest in data-centric design. This course goes beyond simple GraphQL syntax; it explores the real-world problems it was created to solve, along with practical considerations like Resolver structures, the N+1 problem, and Federation. I've structured this course to help you naturally learn how to reduce communication costs between developers and design more flexible API structures.

This course goes beyond simply teaching you how to use Docker as a tool; it approaches the subject from the perspective of solving the real-world dilemmas and problems encountered in professional practice. From unpredictable errors caused by differences between development and production environments, to configuration mistakes stemming from vague concepts of images and containers, and even the anxiety of "how much do I need to know to survive in the field"—this course explains it all based on firsthand experience operating financial infrastructure. Rather than just listing commands, it focuses on real-world cases: why certain structures are necessary, how to design images for easy maintenance, and how to handle containers for stable service operation. In particular, by prioritizing hands-on practice over theory, the course is designed to elevate students from simply "knowing how to use" Docker to "understanding it from an operational perspective" through visual comprehension and direct experience. This course provides practical standards and direction for those new to Docker, those who have used it but lack a clear conceptual grasp, and developers looking to take their infrastructure intuition to the next level.

It was created to solve the "overwhelming problem of not knowing where or how to start with Kubernetes." Based on hands-on experience operating financial infrastructure, it is designed to help you understand the actual build and operation flow rather than just simple theory. Through a learning process that covers the relationship with Docker, YAML, Pods, Deployments, and Services, learners will master Kubernetes not just as a "concept," but as a "usable skill."

Most developers are still stuck on Batch and CronJobs when it comes to data processing. However, in real-world production environments, data is generated continuously, and failing to process that flow immediately leads to latency, bottlenecks, and consistency issues. Having personally dealt with real-time recommendations, state synchronization, and event delay problems in high-traffic environments, I’ve often asked myself, "Is batch processing really the right approach for this?" This course begins with that very question. It explores how to use Apache Flink to perform computations the moment data flows, manage state securely, and produce accurate results based on Event Time—all from a practical perspective. Beyond simple theoretical explanations, you will experience how real-time stream processing systems are designed and operated through actual source code and architectures. For those who found real-time processing vague or were curious about the world beyond messaging, this course will provide a clear sense of direction.

At some point in backend development, you start to have these concerns. It's that moment when services expand and traffic increases, and you begin to feel the limitations of simple REST communication and CRUD structures. I experienced these same issues in the field and went through much trial and error balancing performance and structural complexity. The solution I chose during that process was NATS. Its simple configuration based on a single binary, ultra-low latency performance in microseconds, and the fact that it provides essential features—from Pub/Sub to Queue Groups and JetStream—without being overkill made it a very practical choice for real-world service environments. This course is not just a list of NATS features. Based on the problems I faced in practice, I explain through code and workflows why I chose NATS in certain situations and how I designed the architecture. This course is designed to help everyone—from those new to messaging systems to backend developers preparing for employment and senior developers considering better architectures—understand distributed systems and grow to the next level.

This course explores microservice architecture and distributed environments not as a simple list of technologies, but from a 'design perspective' required in actual work and interviews. Starting from the differences between monolithic and MSA, it progressively covers incremental migration strategies, modular monoliths, clean architecture and hexagonal architecture, clearly explaining why each choice is necessary and the trade-offs involved. Through hands-on practice, you can directly verify the intent of the structure and learn about core issues inevitably encountered in distributed environments—such as data consistency, transactions, inter-service communication, and failure handling—through realistic scenarios. Based on actual questions and perspectives from Kakao interviewers, this course aims to go beyond simple knowledge acquisition and elevate your way of thinking about distributed systems to the next level.

"Just like the real thing! Master job interviews, coding competitions, and your skills all at once." Perfect preparation for corporate coding tests! Improve your skills from basic to intermediate! This course contains only the essentials necessary for coding test preparation. Structured step-by-step from basic concepts to practical problems, you can improve your programming skills and practical sense at the same time.

With step-by-step explanations that even beginners can easily understand, the once-vague coding tests will become clear. Learn only what you need and apply it to real-world practice right away!

CS knowledge lectures on design patterns, networks, operating systems, databases, etc. from the author of the #1 book in Korea, "CS Major Knowledge Notes for Interviews"! Covers all the concepts needed for CS interviews and the latest past questions!

This course allows you to experience a comprehensive list of questions and answer strategies for both technical and behavioral interviews. In particular, the curriculum is designed to help you prepare for interviews by learning—through Q&A—server scaling strategies and large-scale data processing strategies essential for junior-level technical interviews, as well as how to provide the best answers to open-ended questions typically encountered in final interviews.

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

This [Practical Employment] lecture covers only the most practical content. It comprises a lecture + e-book (total 144 pages). 1. This course strategically teaches the entire practical job search process, from interpreting job postings to resumes, cover letters, and interviews. 2. Students will learn to structure and articulate their experiences, and acquire tailored strategies and writing skills for each recruitment stage. 3. Ultimately, you can define your own career direction and complete actionable employment strategies.

We'll tell you what to do and what not to do when you have to give a technical/business presentation.

Based on questions from companies such as Nexon, NCSOFT, Krafton, and Netmarble, this explains core C++ concepts and problem-solving skills that job seekers and career changers must know. Pass your job tests and technical interviews all at once with actual exam questions from the past 10 years.

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

Through this lecture, students will be able to learn the basic and post-processing technology flow of semiconductors, and will be able to learn the content necessary to prepare for interviews at post-processing semiconductor companies.

This course is for job seekers and career-changing backend developers preparing for coding tests with JAVA. We clearly identify question types by analyzing 195 actual past exam questions.

A course that helps you understand core database concepts and trains you to explain them verbally in interviews.

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

This is a game development & algorithm course that focuses on the algorithms and principles of 2D game development from the ground up using Windows API and C++.

This course explores the essential RPG game feature of "pathfinding" while naturally teaching data structures and algorithms. It quickly covers common technical interview questions, allowing you to prepare for coding interviews in a short period.

This is a [Backend, Resume Enhancement] class prepared for job seekers and junior developers.

Hello, I am Gamja, a 4th-year frontend developer. Thinking back to when I first learned JavaScript, I remember many times when I felt like I understood everything while following along with YouTube videos or books, but my mind would go completely blank the moment I opened an empty editor. At first, I was just busy copying and pasting code I found through Googling. Because of that, when an error occurred, I didn't know where to start fixing it, and I would spend several days staying up all night in frustration. That’s when I realized a painful truth: writing one line of code yourself while understanding the principles is more valuable for your actual skills than copying someone else's code 100 times. Many beginners struggle with these concerns in front of the high wall of JavaScript: 🚨 "I made the screen look pretty with HTML/CSS, but I feel lost trying to make it move." 🚨 "I've memorized all the syntax for variables and functions, but I don't know how to combine them in practice." 🚨 "My head hurts just hearing terms like event bubbling or DOM manipulation." That is why I prepared this course. I have organized only the 'surest shortcuts' that I learned through countless trials and errors. While preparing the materials, I didn't list difficult development jargon. I boldly discarded the grammar found in thick textbooks that you won't even use right away. Instead, I will plant the core principles used in practice as naturally as breathing into your mind through intuitive everyday metaphors like 'conveyor belts' and 'paint palettes.' In this course, you won't just learn theory. As soon as you learn the theory, you will build four core UIs that you will inevitably encounter in frontend work—such as accordions, tab menus, and dark mode toggles—from scratch with me. After completing the course, you will no longer be someone who scrapes someone else's code and presses the run button while praying. You will be reborn as a real frontend developer who can design how to structure a screen on your own and write JavaScript code according to your intentions. I have included all of my practical know-how. Don't stop in front of an empty editor anymore. It's time to get started.

✅ Out of the entire series (1) ~ (7), (4) data structure, algorithm, object-oriented, programming language ✅ CS101 series lectures - From basic computer theory to the latest practical examples - Provides a wide range of basic knowledge

This is an online lecture that systematically organizes pathfinding and spatial partitioning algorithms used in game production.

DevOps Interview Preparation: Master your interview preparation for Git, Docker, CI/CD, Terraform, Ansible, Kubernetes, and Monitoring.