Blog

A collection of 110 posts

Vello: Handling External Events Not in Class Path

Vello: Handling External Events Not in Class Path

Problem Definition In the Lakey project, we manage external events using the Vello module of the in-house messaging framework Prologue to store these events and utilize them in the LLM context. The event converter provided by Prologue, 'TypeAwareEventConverter', reads the 'payloadClass' value from the header

Hello AI World !

Hello AI World !

The Reflection of a Lazy Backend Developer Dynamic CMS Design In January 2026, the project I joined after returning to headquarters was the 'Tourism Content Management System (Pinlime).' We were in the process of reworking it on a modern architecture based on a project that had been applied

Implementation of a Flexible Payment Module Using the Strategy Pattern

Implementation of a Flexible Payment Module Using the Strategy Pattern

As we began implementing the payment module, the first concern we faced was not simply 'how to call the payment approval API.' The core issue was 'whether we could provide a consistent payment experience without disrupting the service's payment flow, regardless of which payment gateway

Git Branching Strategy

Git Branching Strategy

1. Introduction It's easy to think of Git branches as just a "tool for dividing features," but in actual work, branch strategy is directly connected to collaboration methods, development environment deployment and testing, QA validation, operational deployment, and hotfix responses. In environments where multiple people are

LLM Automatic Translation: Expanding Nested Objects and List Structures

LLM Automatic Translation: Expanding Nested Objects and List Structures

1. Introduction In the previous work, we dealt with the structure of separating the LLM automatic translation function into an asynchronous event flow. Instead of directly calling the LLM within the save request, we configured it to publish events in situations where translation is needed and perform the translation in

Improving Duplicate API Requests in a React Environment

Improving Duplicate API Requests in a React Environment

As the project size increases, it becomes more important to manage state and handle asynchronous requests efficiently than simply implementing features. Particularly in React-based applications, multiple components share the same data and make API calls based on various state changes, which can lead to unexpected duplicate request issues as

Resource Isolation Strategies for Data Backfill

Resource Isolation Strategies for Data Backfill

1. Introduction: Challenges of Backfill Architecture for Large Data Transfers In modern distributed system architecture, the reliability of data pipelines is directly linked to the survival of services. In particular, time series data generated in IoT, finance, or real-time monitoring systems often requires throughput of tens of thousands of

Improving Review Service Quality

Improving Review Service Quality

1. Introduction When developing a service, there are times when the time spent contemplating the aftermath is longer than that spent implementing the interface. I experienced this while developing the review feature for a recent tourist attraction content service. The review feature allows users to write their own reviews and

Individuals Accelerated by AI, Teams Unable to Digest

Individuals Accelerated by AI, Teams Unable to Digest

- The use of AI has accelerated code and document writing, but it does not directly translate to the team's progress. To connect an individual’s work speed to the team’s productivity, we assess the absorptive capacity required, based on the criteria of detectability, traceability, and recoverability. At

Redesigning MongoDB Online Archive Query Strategy

Redesigning MongoDB Online Archive Query Strategy

1. The Beginning of the Problem: Rising Storage Costs As the service operation period increased, the MongoDB storage capacity also continuously expanded. Due to business requirements, we couldn't delete the already created data, but keeping all the data in regular storage was becoming a significant cost burden. In

JVM Heap Configuration and OOMKilled

JVM Heap Configuration and OOMKilled

1. Overview This project required the introduction of a feature that detects anomalies in ship sensor data and generates alarms. To implement this, a new batch logic was developed to query sensor data for each ship, detect conditions for alarm generation, and then generate alarms. This was executed in a

Loopin Messenger Development Story

Loopin Messenger Development Story

1. Introduction 1.1 Project Background The existing structure of old messaging services struggled to adapt to the changing web environment, leading to many maintenance-related shortcomings. This project, 'Loopin', was initiated with the goal of removing this Smalltalk system and rebuilding it on the latest Vizend platform

How to Choose a DB Schema Migration Tool

How to Choose a DB Schema Migration Tool

Compared Flyway, Liquibase, Bytebase, and Atlas in MSA·DDD environments and summarized what to choose based on different situations. 1. The schema keeps changing without stopping In DDD and MSA, the database schema is not a fixed asset in a cloud-native environment. It keeps changing throughout the operation of

From Planning to Testing: An Experience in the Development Cycle

From Planning to Testing: An Experience in the Development Cycle

1. Introduction The process of delivering a single screen to the user involves more steps than expected. It seamlessly connects the stages from planning, publishing requests, development, to testing. This time, I took on most of the process, excluding publishing, myself. This article reflects on the process rather than introducing

Response Delay Issues Solved with Cache Strategy

Response Delay Issues Solved with Cache Strategy

1. Overview The first challenge I faced while operating the MyData service was the response delay of the main screen that occurred during the rapid increase in user numbers. Initially, the structure did not pose a significant problem, but as the user base grew, it manifested as a noticeable delay.

Experience with OpenHTMLtoPDF

Experience with OpenHTMLtoPDF

1. Introduction During the project, a feature was needed for users to download estimate and document data in PDF format. Initially, it was thought that simply generating a PDF file would be sufficient, but there were several considerations during the actual review process. * Korean output support * Ease of layout modification

Solving MSA Quality Control with CI Gates

Solving MSA Quality Control with CI Gates

1. The reason for placing the quality management system in CI I am currently participating in an MSA consulting role as a DevOps engineer. When it comes to consulting, you usually think of design discussions such as service boundaries or domain separation, but the area I was in charge of

The Standard of Industrial IoT, MQTT

The Standard of Industrial IoT, MQTT

1. Industrial IoT and Data Collection Recently, IoT technology is being used for various purposes such as monitoring equipment status, analyzing production data, and remote management in manufacturing sites. Equipment such as PLCs, sensors, and robots continuously generate data, and effectively collecting and utilizing this data is one of the

Unifying Code Style with ESLint and Prettier

Unifying Code Style with ESLint and Prettier

1. Background In the previous article, we discussed the physical structure design based on Monorepo, and this time we will talk about how to unify code writing rules among developers who write code on top of it. As the project scale increases, it has become common for multiple developers to

Fixture-based Test Data Configuration

Fixture-based Test Data Configuration

1. Introduction When progressing through a project, there are many times when we realize that "we need to write test code" but end up postponing it due to scheduling pressures. I was no exception. While developing backend services, initially, I was manually verifying functionalities through Insomnia or screens

Who Ate All the Tokens?

Who Ate All the Tokens?

When utilizing LLMs for work, it initially seems most important to write prompts as short and clear as possible. I also thought at first that I could just shorten the sentences I input to save tokens. However, my perspective changed while using agent-type development tools like Codex. In reality,

Requirements, IA, and Flowchart Creation

Requirements, IA, and Flowchart Creation

1. Introduction: The planner designs 'processes' rather than 'screens'. In the IT industry, the role of a service planner is often misunderstood as that of someone who "sketches and draws screens". This is because tasks involving design tools to place buttons and create wireframes

Survey Management Service Implementation Case

Survey Management Service Implementation Case

1. Project Background and Technology Selection The survey service is the core service of a medical survey platform that deals with Patient-Reported Outcomes (PRO) reported directly by patients, managing the entire life cycle of surveys from defining the survey format to sending, collecting responses, and closing. Scoring, statistics, and

Improving Maintainability with Reusable Design in Devlime

Improving Maintainability with Reusable Design in Devlime

1. Background Devlime development was conducted in a way that multiple developers work simultaneously, each responsible for their own features and domains. Since it is based on the Vizend platform, the project structure and basic development methods were somewhat unified, and the overall architecture was well established. However, as the

A Review of React Query Cache Strategies

A Review of React Query Cache Strategies

1. Introduction: When does Server State become stale? When running the frontend, there are two types of reports that you will repeatedly hear from users. One is, “I just registered, but it’s not showing on the list,” and the other is the opposite, “I was idle, but the screen

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