Practical MySQL Locks and Deadlocks for Spring·JPA Developers — Reproduce and Fix Production-Only Hangs with Code

Solve the common codes, category hierarchies, history tracking, soft deletes, statistics, dynamic design, JSON utilization, and more that you inevitably encounter in real-world design through nine core patterns. This goes beyond simple theory, incorporating practical know-how proven across numerous projects and criteria for making the right choices in different situations. Become a true design expert who can confidently design for any requirement.

I have created a course titled 'Introduction to MySQL Performance Optimization & Practice (SQL Tuning Edition)' that is easy for non-majors to understand and can be applied immediately in practice!

This course develops a REST API that satisfies Self-Descriptive Message and HATEOAS (Hypermedia as the engine of application state) using various Spring technologies.

This course goes beyond basic CRUD-level database usage, helping you develop the PostgreSQL skills needed in the AI era from a practical, real-world perspective. Drawing on AI development experience in Silicon Valley, you’ll gradually learn how to design and use JSON, indexes, transactions, and pgvector in actual services, while gaining the skills to solve complex data structure and performance problems.

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

We covered the concepts considered while migrating 20 billion data items managed through the existing MongoDB to MySQL.

As you work in backend development, you eventually find yourself facing a certain concern. As services multiply and traffic increases, there comes a point when simple REST communication and a CRUD-only structure begin to show their limitations. I experienced the same problem in practice and went through many trials and errors trying to balance performance with structural complexity. The solution I chose in that process was NATS. Its simple, single-binary-based setup, ultra-low-latency performance measured in microseconds, and practical feature set—from Pub/Sub and Queue Groups to JetStream—made it a highly realistic choice for actual service environments. This course is not about listing NATS’s features. Based on the problems I encountered in practice, it explains through code and workflows when and why I chose NATS and how I designed the architecture. From those new to messaging systems, to backend developers preparing for employment, and senior developers considering better architectures, this course will help everyone understand distributed systems and grow to the next level.

From the fundamentals of MySQL usage to the advanced techniques required in real-world service environments, you will learn progressively. The course also covers a wide range of topics, including data modeling techniques based on various cases and practical data, evaluating the effectiveness of Foreign Key design, analyzing the Google Calendar schema DDL, and modern DDL design principles. It provides an in-depth understanding of how to use MySQL as a core component of a system, rather than merely as a database.

Regardless of the field! This is a lecture that covers the core fundamentals that developers must know in practice in an easy + code-oriented way. I highly recommend this lecture to all junior developers and job seekers who want to grow.

Secrets of people who are good at their jobs! How should I start with SQL? It covers everything from SQL installation and basic environment configuration to simple practical exercises that can be used in real life! You can also learn basic commands step by step through practical exercises.

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.

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

Building your own emotional diary service with Spring AI + React It's time for our 4th project with Neo + Essential!

I have created an 'Introduction to Elasticsearch' course that is easy for non-majors to understand and can be applied immediately in practice!

"SQLD is an exam where past questions are not released." In preparation for the upcoming 62nd exam (2026.08.22)- Practical materials featuring 50 questions per subject and chapter, vividly reconstructed by directly recalling the latest 61st exam!

A Redis course created with a current Kakao interviewer. From hands-on practice with data structures ranging from String to Sorted Set to Sentinel and cluster configuration, you’ll build design rationale that holds up in interviews and real-world work.

Not only developers, but also planners and data analysts learn databases step by step, starting with the basics of SQL.

Learn how modern data teams leverage dbt. Build maintainable analytics models and validated data pipelines hands-on. Master core concepts of analytics engineering with a practical focus. This course is for those who want to take their data career to the next level 🚀

From Docker, Kubernetes to microservices, CI/CD, and service mesh, you can easily learn not only the basic theory but also the actual application implementation through examples. By organizing only the core contents necessary for actual use, it provides a starting point for learning about the element technologies covered in the lecture.

When fixing legacy Java code, determine what to change and which behaviors to preserve. In the existing IntelliJ IDEA hands-on exercises, you directly review code changes, while in the 16 newly added theory lessons, you learn about names, functions, duplication, responsibilities, calling contracts, and validation criteria.