Dolphin-Friendly Spring Boot 3 + PostgreSQL 17

Build your coding skills by implementing data structures in Java from the ground up.

Through this lecture, even non-majors can fully understand the concepts and operating principles of the MVC module, which is the core of Spring.

Spring Web Programming learned while creating a calendar (schedule management)! Completely master Spring with examples you can use right away, not just short snippets~

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.

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.

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.

Even people who are studying Java for the first time can easily understand it. You'll learn Java through theory with rich explanations and hands-on practice.

Did you give up while studying Spring? Even complete beginners new to coding and non-majors can make it from JSP to Spring Boot without giving up - we'll open the path to Spring Boot for you.

We develop a chat service using web socket/stomp and springboot. We also configure a simple screen using vue.js, which is a relatively easy framework. We also configure multi-server scalability design using redis pub/sub.

Handling media (video, audio) on the web is now easier than ever! Learn the MediaStream API and WebRTC by following along step by step.

Based on an understanding of Reflection and Annotations, it helps you clearly understand how the Spring framework operates!

Have you ever wondered "how" the many Java libraries and frameworks you use provide this functionality? In this course, learn how to manipulate various codes or objects provided by Java and take your Java skills to the next level.

💡 Even non-developers can go from startup MVP to monetized service in just 10 hours with AI! 💰 Development that used to cost tens of millions in outsourcing fees now completely solved for 120,000 won 🎯 Complete 5 real business projects including business card recognition, sentiment analysis, and location analysis 🔥 If you're a planner, marketer, or aspiring entrepreneur, implement ideas without developers ⚡ Start now and acquire lifelong development independence skills!

This course is a systematic learning process for general login, social login, and JWT-based token authentication using Spring Boot 3, Spring Security 6, and React. It covers building OAuth2 social login and security-enhanced JWT authentication systems in both MPA and SPA environments, while addressing overall security practices such as XSS/CSRF countermeasures, HTTPS application, token reissue and revocation strategies, and secure secret key management. You will practice configuring production-level environments, including building and deploying via AWS and performance optimization using Redis. Through the completed project source code provided in the course, you can understand the entire login flow and apply it directly to real-world practical work.

AI is no longer a choice, but a matter of survival. Shorten development tasks that used to take 3 days down to 30 minutes; leave repetitive tasks to AI and focus on solving more important problems. Through AI-native development methods that are practical rather than theoretical, we will show you the definitive way to be recognized as an "AI-savvy developer" at your company.

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!

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!

The most definitive practical guide for developers who want to integrate AI into their Spring projects right away! Beyond simple LLM API calls, you will perfectly master building production-level AI environments that can be immediately applied to real business logic using RAG and MCP.

We will show you how Java backend developers using IntelliJ can maximize their productivity with Claude Code. In particular, we help you perfectly resolve the vibe coding environment issues faced by those using Windows environments.

Learn how to save, modify, delete, and query data in a database. Anyone, regardless of major, can easily follow along in just 30 minutes.

Experience the power of Type Safe SQL with jOOQ!