Kakao Interviewer's Hands-on Spring Batch: Everything About Large-Scale Data Processing

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 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.

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.

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.

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.

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."

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 covers RPC communication techniques to maximize performance in large-scale MSA (Microservice Architecture) environments. Beyond simple gRPC practice, you will learn how to implement stable and efficient inter-service communication in real-world production environments where hundreds of microservices operate simultaneously. Based on Golang, the curriculum focuses on practical applications, including writing Protocol Buffers (proto) syntax, automated code generation and service implementation, the structure of gRPC and its advantages over traditional RPC, and performance optimization strategies. Designed to be easily understood even by non-majors or entry-level server developers, the course explains everything from the basic concepts of RPC to the internal workings of gRPC step-by-step, helping you build practical skills that can be applied immediately to real services.

Systematically learn the distributed NoSQL database Cassandra, from basic concepts to practical application. Develop high-volume data processing capabilities through practice-oriented theory and hands-on exercises, including data modeling, query optimization, and cluster configuration. Even without prior database experience, you can grow into a Cassandra expert based on the know-how of a current 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 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.

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.

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.

This is a Redis course created with a current Kakao interviewer. It covers everything from data structure practice (String to Sorted Set) to Sentinel and Cluster configurations, helping you build design rationales that work in both interviews and real-world practice.

This course was created to solve a common problem many people face while preparing for developer jobs: "I studied CS and data structures, but I get tongue-tied during interviews." While conducting actual interviews at companies like Naver, Kakao, and Toss, I noticed that most candidates have memorized concepts but cannot explain why those concepts are necessary or how they are applied in real-world situations. Rather than simple rote memorization, this course teaches you how to understand the interviewer's intent and provide more persuasive answers to the same questions. Whether it's the OSI 7 layers, data structures, or coding tests, we focus on why you need to know them, when they are used, and how to speak about them to receive a positive evaluation in an interview. This course is for those who want to become developers who can explain what they understand in their own words, rather than just giving the same answers as everyone else.

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 breaks down microservice architecture and distributed environments not as a mere list of technologies, but through the "design perspective" required in actual practice and interviews. Starting from the differences between Monolithic and MSA, it covers gradual migration strategies, Modular Monoliths, Clean Architecture, and Hexagonal Architecture step-by-step, clearly explaining why each choice is necessary and the resulting trade-offs. Furthermore, through hands-on practice, you can directly verify the intent of the structures and learn about core issues inevitably encountered in distributed environments—such as data consistency, transactions, inter-service communication, and fault tolerance—through realistic scenarios. Based on the actual questions and perspectives of a Kakao interviewer, this course aims to go beyond simple knowledge acquisition and elevate your very way of thinking about distributed systems to the next level.

This course provides a step-by-step learning path, ranging from the fundamental usage of MySQL to advanced techniques required in real-world production environments. It covers a wide range of topics, including data modeling techniques based on various case studies and practical data, evaluating the effectiveness of Foreign Key designs, analyzing Google Calendar schema DDL, and modern DDL design principles. Through this course, you will gain an in-depth understanding of how to utilize MySQL as a core system component rather than just a simple database.

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 goes beyond explaining the concepts of Spring Batch and covers how to actually integrate Spring Batch into a service that is already running. Based on structures used in real-world practice, you will learn by directly implementing everything from Batch Job configuration and execution flow to data processing structures. Rather than simple examples, it provides step-by-step explanations based on professional architectures, covering Batch Job configuration, execution flow, and data processing structures. In particular, we focus on: How to connect Batch to an existing Spring Boot service and how to build a structure that can be operated stably. Through this course, you will: ✔ Be able to build Batch directly into existing services ✔ Be able to design large-scale data processing structures ✔ Reach a level where you can apply these skills immediately in the field 👉 This is not a "theory lecture" 👉 This is a practical course on integrating it into actual services

"Let's master Spring Batch once and for all. Putting an end to the dark ages of batch code.💀"

This course will help students understand Java classes in more detail and use them more naturally. This will lead to more object-oriented programming.

A Java advanced project course for beginner developers who want to develop practical skills! We'll build a console-based kiosk ordering system together using Spring Core, JdbcClient, and H2 DB.

This course provides an in-depth study of multithreading and concurrency, from basic principles to practical applications.

The flower of Java programming, object-oriented programming! Concepts and practice. We will teach you at the same time.

Are you lost while learning web development? I'll help you find your own way. Even if you're not from a computer science background, you can understand how web service architecture works through a short 1-hour lecture.

3D Globe Article Service with ThreeJS and SpringAI | Neo + Essential Create your own 3D globe article service using your personal chatbot and ThreeJS!

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.

Currently, Android can be developed using the Java and Kotlin languages. You can develop the same Android applications regardless of which language you use. This course covers most aspects of Android application development, from basics to advanced levels, and all code is written using the Kotlin language starting from the fundamentals. Furthermore, it utilizes Google's latest UI library, Material 3. This course primarily focuses on menus, Android application components, threads, and fragments within the overall Android curriculum, and more in-depth topics will be covered in the next course. Soft Campus will always strive to provide the latest lectures. Thank you.

Knowing design patterns will make it easier to learn not only Spring but also many other technologies and programming languages. It will also help you develop more flexible and reusable object-oriented software.

Create your own visual novel game using React, Javascript, SpringAI, and Springboot. Learn how to make a web-based visual novel game with SpringAI and React! Neo + Essential

Channel Talk interviewers will directly analyze the difference between failing and passing answers to the same question and help you prepare for actual follow-up questions.

Learn Springboot + iOS RestAPI Board Creation Faster Than Anyone Develop a CRUD server with Springboot and create your own board with iOS!!

Learn Springboot + React RestAPI Board Creation Faster Than Anyone Develop a CRUD server with Springboot and create your own board with React!!

In this course, rather than directly covering theory, you will learn how to effectively use Redis in code through hands-on practice.

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

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

Software development roles in the defense industry: ✔ Have different hiring criteria compared to general IT companies ✔ Use specialized tech stacks and development methodologies ✔ Offer very little information on how to effectively highlight your major, career, and projects. This course: 👉 Provides the perspective of a software developer who has experienced actual defense projects and hiring processes 👉 Explains how defense companies evaluate software developers 👉 Focuses on specific case studies to show you how to prepare your resume, interviews, and projects to increase your chances of success. This course transforms the state of "wanting to become a defense software developer but having no idea what to prepare" into a "clear roadmap you can start following right now."

The TDD & Clean Code masterpiece lecture, recommended by many senior developers in Korea to junior developers for over a decade.