Koki Kato

Please introduce yourself.

My name is Koki Kato. In 2019, I completed my master's degree at a graduate school and joined LINE Corporation as a new graduate. As a server-side engineer, I build and operate Apache HBase (hereafter HBase) clusters used on the server side of the LINE Messaging Platform. For the last six months or so, I have also been in charge of creating a system for linking IDs and data, accompanied by the reorganization within the Group, mainly involving LINE Corporation and Yahoo Japan Corporation.

When I was in college, I majored in information science and researched automatic detection of software bugs. I was looking for a job with the aim of becoming an engineer, and there are several reasons why I chose LINE Corporation.

First of all, the job here enables us to handle services that are used by people of all ages and genders. And because so many people are using it, engineers are required to apply technical ingenuity to handle large amounts of access and data. That is a very rewarding aspect of our job. I used to do programming as a hobby, but I thought that if I was joining a company, I wanted to challenge myself to do something I couldn't do alone.

Before I entered the company, I read interviews and columns by LINE engineers discussing 1how they built a system capable of handling XX million requests per second. I thought it would be interesting to be able to handle access on such an immense scale, and that was one of the reasons why I joined the company.

Could you please describe your main responsibilities and the specific workflow you follow?

I’m primarily in charge of three tasks. First is the operation, monitoring and enhancement development of HBase. Currently, I am involved in a project to migrate to SLO-based monitoring, where I oversee the design and implementation.

We provide the HBase platform for a variety of systems within the company. We try to make the platform as highly available as possible, but there is a chance that something will go wrong and the system will become temporarily unresponsive. Given that, setting unrealistic SLOs will overload our engineers in their operations. Therefore, we consider and set what SLO is appropriate, and we are working to improve the system and operation flow based on the indicators.

The second task involves redesigning how the LINE social graph is handled. My team not only builds and operates HBase clusters, but also takes ownership of how the LINE app's user data is stored in the first place. In this project, we are redesigning not only the internal part of the server, but also across the server and the client. Currently, we are trying to make a major change in the data design for handling the social graph of the LINE app. Conventional designs have problems such as difficulty in analyzing data and poor performance. Therefore, we are working on a project to improve the problems of the old design. The challenge with this project is that it needs to be able to move to a new data model while maintaining performance and data consistency without any downtime for the LINE app.

The third task is the development of an account platform that links IDs and data among LINE Corporation, Yahoo Japan Corporation, and other Z Holdings group companies. Specifically, I am in charge of the design and development of an ETL system for sending user data and logs of linked services to the analysis system.

Example of a Daily Schedule

• 10:00 am

  Start work, and check messages, and review code

• 10:30 am 

  Work on development tasks

• 1:00 pm

  Lunch

• 2:00 pm

  Chat with the team over Zoom and support new members

• 3:00 pm

  Attend a meeting for a data integration project due to the company merger

• 4:00 pm

  Work on development tasks, write documentation, have Slack discussions, and review code

• 7:30 pm

  End of work

The schedule is just an example, but I allocate tasks by myself on a daily basis while looking at the balance of the three types of work mentioned earlier.

What do you keep in mind at work?

Whenever I work on something, it is important to clarify "why we are doing it," "how we are doing it," and "what kind of results have been achieved," and to communicate that to other stakeholders. Visualizing this information offers several advantages: it makes it easier to seek opinions and cooperation from those around you, helps in adjusting the priority of each task, and clarifies your goals so that you can take the shortest route to solve them.

In addition, it is important to keep a record when conducting various investigations and examinations. Records make it easier to gather ideas from others, and leads to a smoother retrospective when referenced.

Please share your experiences of what has been interesting or challenging in your field of work.

When operating a database that handles a large amount of data, we are likely to encounter many unforeseen problems. For example, problems can be caused by faulty hardware, and sometimes it can be very difficult to reproduce an issue. We also face performance issues frequently. Since the LINE Messaging Platform is a distributed system, it is also essential to consider how to ensure data integrity.

It is an environment where we encounter unforeseen edge cases and face issues that require us to learn new knowledge every day. It's demanding, but I enjoy it every day because this is the kind of work that drove me to join the company.

What is the most rewarding part of joining the company?

I enjoy building and operating middleware such as databases rather than developing service functions. When we're dealing with large amounts of data, we're often faced with technical challenges that aren't common in a typical company.

In doing so, we need to make full use of our engineering knowledge to come up with solutions. It’s a rare experience, and it is an aspect that makes me glad that I joined the company.

In addition, engineers from LINE Corporation and Z Holdings Corporation, who collaborate across the company to integrate systems related to the account platform, are all specialists. In reviews and meetings, they always share knowledge and perspectives that were entirely new to me, and I feel that I am growing as an engineer through the extensive feedback I receive. There are many opportunities for engineers on the team to discuss how to improve design and implementation, which serves as a stimulus for my work.

This is a typical example, but by becoming LY Corporation after the merger, the size of the company will be even larger, and the number of experts in various fields will increase more than ever. Since we each build our own private cloud, we have experts in related technologies such as virtualization, as well as in the JVM (Java Virtual Machine), given our use of Java. It's hard to meet people who are familiar with these technical fields in ordinary companies, so it's interesting just to talk to them, and I'm learning a lot from them.

What are your expectations for LY Corporation, and what are you looking forward to in the future?

As we carry out the reorganization of the Group centered around LINE Corporation and Yahoo Japan Corporation, the systems in use, as well as the knowledge and know-how, will be shared across the organization. We want to use those assets to improve our services, and we hope to build an even better platform.

Currently, I am involved in development work with engineers at Z Holdings, and there are several aspects that I find rewarding in my work. First of all, members from different corporate cultures are working closely together to gradually align their understanding as they proceed with the project.

In addition, the construction of an ETL system for data linkage demands high security requirements. To overcome various constraints and integrate data, it's essential to consider many factors in design and implementation. As an engineer, I enjoy exploring potential methods.

When handling these tasks, we need to change some of the approaches we were accustomed to using in previous projects. In the past, we worked on projects with team members from within LINE Corporation who knew each other relatively well. As a result, projects ran smoothly without the need for consciously aligning perceptions.

However, when multiple companies merge, it is necessary to work on projects with people from different cultures and environments while ensuring everyone is on the same page. We need to effectively organize everyone’s opinions and work in a way that everyone can agree on. This is something that I have not been able to experience in my previous environment, and I have been learning a lot from it.

What are your future goals?

First of all, I want to make sure that the project I am in charge of will be a success. Also, in my career so far, I have never had the experience of building a large-scale system from scratch, so I would like to be involved in such projects in the future. In relation to this, I aim to accomplish difficult tasks that I couldn't achieve on my own, either by collaborating with those around me or by taking the technical lead myself.

Please share a message to our readers

This is especially true for my team, but when I work, I am very often faced with difficult challenges that require all aspects of computer science knowledge. Even as a young engineer, if you have the skills, you will be actively entrusted with such tasks. I believe it's an interesting workplace because it allows you to take on challenges. I’m sure it will be a great environment for honing your skills as an engineer.

• Engineer
• New Graduate