Hi! My name is Toru Kobayashi (@koba04), and I joined Mercari in January of 2024 as a frontend software engineer.

I currently work as a web architect and engineer on the Design System Team. At my previous workplace, my main role was that of an engineering manager, leading projects and handling evaluations, but now I work as what we call an “individual contributor” here at Mercari.

Outside of work, I contribute to open-source software (OSS) and help maintain React libraries as well as the official Japanese website for React.

Developing design systems for future business growth

On the Design System Team, which is the main team I am a part of, we are currently developing the design systems that are used by the services Mercari provides.

Design systems are defined UI components, covering aspects from user experience to use of color, based on Mercari’s design principles. The use of design systems in teams across Mercari allows us to implement features on our application in a way that is efficient and consistent with our design principles. In addition, we are also working to improve accessibility so that our services can be used by anyone and everyone.

When I first joined the company, I was working simultaneously on tasks for both the Web Architect Team and the Design System Team. Both of these teams are oftentimes working on the code for Mercari’s web application as a whole, which requires a wide scope of knowledge. It was challenging at first, but with the support of other members, the experience allowed me to acquire comprehensive knowledge of our application.

Mercari’s web application is actively developed by a multitude of teams. If each team introduced their own libraries, there would be a lack of consistency in our implementation, and the large number of libraries would cause a drop in performance. The Web Architect Team is responsible for the architecture of this application. While it’s challenging to think about the design of such a large-scale application, it also comes with a lot of learnings. Our application also uses some of the open-source libraries that I’ve helped to develop, and I’m able to leverage my past development experience when implementing updated versions of these libraries.

With regard to our design systems, we also work to improve them based on feedback from our product teams. When I joined Mercari, the company was reworking its internal implementations of the components we were providing as design systems, and I helped with these efforts, as well as with implementing these components into Mercari’s web application. The components we provided as design systems were used in various places throughout the application, so it was a difficult task to check for issues arising as a result of the reform, but with the cooperation of the engineers on the product teams, we were able to successfully complete the reform process.

On the Design System Team, we are currently revisiting our existing design systems and working on developing ones that can support us into the future as we expand our business globally and to multiple products. To achieve this, we need to provide both a unified user experience and flexibility simultaneously, which is an extremely challenging task. Developing design systems requires not only the technical skills for implementation, but also an understanding of the product and the Mercari brand. That’s why we discuss what components and design tokens are needed for us to create design systems that will allow us to select technologies, design, and implement in a way that considers our future frontend paradigm and the future of our product.

Mercari is a place where I can “be the worst”

When I was searching for a new job, I spoke with various companies besides Mercari. In the process, I thought about what was truly important to me.

One of the biggest reasons I ultimately chose Mercari was because I resonated with the mission to “circulate all forms of value to unleash the potential in all people” and wanted to work toward achieving that mission on a global scale with diverse members of varied backgrounds and ways of thinking. I was also attracted to the opportunity to be able to impact society through a product.

Mercari is larger in scale than any company I’ve worked for before, and I feel both challenged and comforted by the organization’s fast pace and focus on the product. At Mercari, the company, each team, and each individual sets OKRs (objectives and key results) every three months. Many of the OKRs that are set here are goals that my past self would have thought to be impossible; we are constantly expected to aim high. Even in setting personal OKRs, members are expected to consider goals that add value to the product.

I always keep in mind the words “be the worst” from The Passionate Programmer by Chad Fowler. Mercari is an environment in which I am able to “be the worst” on the team and learn lots from my teammates every day.

Moving forward, I will continue working on creating a product that can scale without sacrificing speed as part of both the Design System Team and the Web Architect Team. Design systems are precisely what play a role in helping us achieve this, and in the future I plan to proactively propose and work on efforts around our application architecture as well.

A stimulating environment for passionate product development

Mercari is the first company I’ve worked for with an English-speaking work environment. During my first few months here, I had to learn things I didn’t know in a language I wasn’t used to, and honestly it was really tough.

Even today, my English still has lots of room for improvement, but I can tell that I’m gradually getting better. The Design System Team has members who are more comfortable in English and members who are more comfortable in Japanese, so we all keep “yasashii communication” in mind and use simple language that is considerate of the listener in discussions. However, to lead projects this is not enough, so I plan to take advantage of Mercari’s English learning program to improve my English further.

From the outside, Mercari as a product may seem well established already, but the truth is that we are still in the stage of taking on various challenges toward achieving our mission to “circulate all forms of value to unleash the potential in all people.”

To do so, it is necessary to create a platform that can support these endeavors. Currently, a project we call the “Golden Path” is underway for the very purpose of supporting our global expansion. This project aims to create unified development processes and architecture across all our companies, and I am truly inspired by such an environment in which we can take on highly challenging projects toward an exciting roadmap.

Something that left an impression on me when I joined Mercari was how many members love the service the company provides. It reminded me of just how passionately people can work on developing a product when they are users of the product themselves.

I also noticed how many members are adept at getting others involved and embody Mercari’s value of “All for One” when working on projects. When members notice something that needs to be done, even if it is outside the scope of their daily tasks, they will create a design doc, get feedback, and arrive at a consensus to move the project forward. I find such an environment to be extremely stimulating.

I look forward to “being the worst” and learning and growing while working with members who truly focus on the goal!