jOOQ in action! Type Safe SQL with Java

This is a practical backend course designed to cultivate the service planning and design thinking skills that developers need in the AI era.

Solve everything from the basics of querydsl to practical use all at once!

I've created a 'MySQL Performance Optimization Beginner/Practical Course (SQL Tuning Edition)' that's easy to understand even for non-majors and can be immediately applied in real-world situations!

Learn about Race Condition, a representative concurrency problem. Practice by comparing single server environments and distributed environments that cause concurrency issues. Understand transaction boundaries and isolation levels. Learn the differences between optimistic locking, pessimistic locking, and distributed locking.

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.

I've created an 'Introduction to Elasticsearch' course that even non-majors can easily understand and apply directly in real-world situations!

This is a course for job seekers / career changers preparing for coding tests in JAVA as backend developers. We analyze 195 actual exam questions to clearly explain the question types.

With the price of a chicken combo, you'll learn the deployment process in order: Spring Boot manual deployment -> Docker deployment -> Github Action CI/CD!

For those aspiring to be Java-based Spring backend developers, to easily secure a job, we learn Java properly! Rigorously!

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

Building Your Own Emotional Diary Service with SpringAI + React This is the 4th project time creating together with Neo + Essential!

When you're doing backend development, at some point you face this dilemma. As services grow and traffic increases, there comes a moment when simple REST communication and CRUD structures feel limiting. I experienced the same problem in real-world work and went through many trials and errors between performance and structural complexity. The solution I chose in that process was NATS. Its simple configuration based on a single binary, ultra-low latency performance in microseconds, and the fact that it provides just the right amount of essential features for real work—from Pub/Sub to Queue Groups and JetStream—made it a very practical choice in actual service environments. This course is not about listing NATS features. Based on the problems I faced in real work, I explain with code and flow diagrams which situations led me to choose NATS, why, and how I designed the architecture. This is a course designed to help everyone—from those new to messaging systems, to backend developers preparing for jobs, to senior developers contemplating better architectures—understand distributed systems and grow to the next level.

# Building an 'Intelligent Collaboration' Expert Agent Team Using Spring AI Router Pattern + RAG + MCP Beyond Single Agents to Architecture: The Definitive Guide to Router Pattern and Agent Isolation Design

We conduct app log analysis using data from Google Analytics 4 and Firebase. It includes useful content for practical use, such as arrays, window functions, funnels, retention, Google Sheets, and more.

It covers just two things properly: object-oriented programming and the JVM! Plus, it throws in linked-list-based linear data structures.

Spring AI + JPA + MySQL Premium Reservation Agent Backend Development with 'Autonomous Behavior' Beyond Chatbots to Agents: The Definitive Guide to Tool Calling and Prompt Engineering

Extract and utilize data through Oracle 18c and become a database expert!

By implementing various practical data analysis cases using SQL, you can simultaneously improve your data analysis and SQL utilization skills.

This course is a practical-focused learning program for JWT-based token authentication and security enhancement techniques that are essential in modern web service environments. Using Spring Boot 3, Spring Security 6, and React, you'll implement secure login systems and cover comprehensive security practices including XSS·CSRF countermeasures, HTTPS implementation, token reissuance and revocation strategies, and secure secret key management. Additionally, you'll practice real service-level environment configuration through AWS build·deployment and performance optimization using Redis, and the complete project source code provided in the course can be directly applied to real-world work.

You can try using jOOQ, a data access technology, and experience Spring development with Kotlin.