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

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."

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.

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.

Kotlin mastery via virtual payment server course.

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.

You may have felt frustrated using Redis without being able to explain why it should be designed that way or why certain patterns emerged. Through my experience in both practical development and as an interviewer, I have treated Redis not just as a simple cache, but as a core component that determines service stability and scalability. This course is not about memorizing commands; instead, I will share my experiences on which structures to choose in real traffic environments and their trade-offs, helping you establish the criteria to explain these concepts confidently in both interviews and practical work.

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!

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.

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 covers RPC communication techniques that maximize performance in large-scale MSA (Microservice Architecture) environments. Going beyond simple gRPC practice, you'll learn how to implement stable and efficient inter-service communication in real production environments where hundreds of microservices operate simultaneously. Based on Golang, the course covers Protocol Buffers (proto) syntax writing, automatic code generation and service implementation, gRPC structure and advantages over existing RPC, and performance optimization strategies with a practical focus. To ensure easy understanding for non-majors and server development beginners, the course provides step-by-step explanations from RPC concepts to gRPC's internal operating principles, enabling you to develop practical skills that can be immediately applied to real services.

You can learn about JWT and ws communication using Spring Boot, and how to handle high TPS.

I am covering the know-how on how I studied and got a job, starting as a non-major.

I'll show you how to use Redis effectively, along with its precautions and best practices, using real-world examples from actual work environments and well-known case histories.

You can learn how to send emails using AWS and Spring. Through this, you can study how to create an email verification system.

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.

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.

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.

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.

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.

A coding test lecture taught by a world competition finalist! Now, stop solving by intuition and start solving with confidence!

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 is a practical technical interview strategy lecture shared directly by a Technical Director who has conducted over N,000 technical interviews. There is no such thing as a "guaranteed way to pass" or a "guaranteed formula for success" in this world. I will show you the interviewer's perspective—how they perceive a resume during the preparation stage, and what they focus on and prioritize during the interview process. A technical interview is not a memorization subject with fixed answers. The core of this lecture is understanding the essence of the process itself: showing your true self to the interviewer and persuading them. Whether you are an experienced professional or a newcomer, this lecture will be helpful for any developer who has ever worried about technical interviews.

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.

Slowly study the C language, which includes the basics of program development that developers need to know.

A course where you understand the core concepts of Java and Object-Oriented Programming (OOP), and even train to explain them verbally in interviews.

Based on my experience starting as a non-major and working my way from startups to major corporations, I have compiled job search strategies and execution methods that have proven effective in practice.

Master Algorithm Problem Solving with 100 Essential Silver Level Problems from Baekjoon Online Judge

For those who have chosen a career in information security/information technology and are preparing to move to large corporations/financial institutions, we will reveal our strategy for passing the exam. A current CISO who has personally recruited and recommended numerous people will share his secrets for passing the exam. He has heard from his acquaintances, security company CEOs and executives of large companies, and compiled a recruitment bible by collecting a vast amount of recruitment secret data.

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

From documents to interviews, the A-Z of designer employment is included. We will show you in detail how to increase your chances of passing by watching the interview process of an actual applicant that you cannot see anywhere else.

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

Have you learned JavaScript but find yourself stuck when it comes to actual projects? I created this course for those who can use forEach but hesitate to use reduce, find asynchronous code a headache every time they see it, and build components without knowing the underlying reasons for their structure. This course doesn't just explain syntax. It focuses on "why we use it this way" to help you develop the coding intuition needed to jump straight into real-world work.

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

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++.

I worked at a company called Algolia in France from 2019 to 2022. I would like to share the reason why I applied to this company, the process of moving, and what I learned and my thoughts. This is not a video like "Secrets to Successful Overseas Employment" that can be applied to everyone. However, I hope that this video, which details my personal experience, will be a good hint to many people.

When learning Swift, the iOS programming language, it can be confusing when multiple concepts appear all at once. That's why I created this course with the principle that "when understanding a new concept, only previously learned concepts should be used." So this course is meticulously designed with a sequential structure between concepts, where only one new concept appears at each stage, and no other unfamiliar concepts appear at all. One concept per minute, 180 concepts total. From the basics of variables and constants to understanding memory structure from a CS perspective, and even the latest syntax for asynchronous processing. In 3 hours, you'll learn 180 core concepts in the designed order.

Do you feel overwhelmed just thinking about the moment of persuasion? Stop relying on emotions and intuition for negotiations! With former Apple business coach Jasmine Han, you can take control of negotiations in just 15 minutes a day for one month.

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

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.