Personalize to globalize:How Mercari is reshaping their app, their company, and the world

Mercari, a marketplace app with 19.04 million monthly users in Japan (FY2021 as of the third quarter), has experienced a significant diversification of its user base since its release nearly eight years ago. The company believes that, to keep these users with extremely varied and wide-ranging preferences, personalization is key.

In 2019, the company established a team responsible for the development of features for personalization. What does an “extremely user-friendly” app look like to Mercari? We asked two leaders in charge of the company’s Personalization Team, a part of its development organization made up of developers, nearly half of whom hold non-Japanese citizenship.

※This article is a repost from Newspicks

Featured in this article


  • Aki Saarinen

    Director, Mercari Customer Experience and Data Team
    Aki discovered programming at the age of eight and has aspired to create amazing products ever since. He joined Mercari in October 2019 and currently serves as the Head of Product, Marketplace where he leads a team with dozens of members in close coordination with a number of other technical and data analysis teams.


  • Snehal Shinde

    Mercari Engineering Manager. Snehal joined Mercari in December 2019 after being involved in building mobile applications and business software for a variety of industries, including the automobile industry, healthcare industry, and gaming industry in her previous job. She currently serves as the Engineering Manager for two development teams comprising both Android and iOS engineers.


We Challenge Ourselves Because the Work is Far from Done

── Having tried the app, I find both buying and selling to be easy enough. Frankly, the product seems pretty complete to me already.

Aki: At Mercari, our mission is to create a global marketplace that generates new value. We’re trying to build a recycling-oriented society around the world, one where things we have buried away in our homes can be valued and reused.
However, compared to the global population of 7.9 billion, Mercari’s number of MAU (Monthly Active Users) is still just 19 million. That’s a ratio of 0.2%. Looking at it this way, we see ourselves as only 0.2% of the way to completing our product mission and still brimming with potential for growth.

── What is it, in particular, that’s lacking?

Aki: Let me answer a question with a question: how do you use the app when you are shopping on Mercari?

── Hmm… I’d say, most of the time, I think of something I want, search for it, choose something from the results, and buy it.

Aki: Right. Mercari currently has 19.04 million users in Japan, with a cumulative total of more than 2 billion listings (as of December 2020). So as long as you search with the right keywords, you’ll usually find what you’re looking for.

But it might not be so easy for someone using Mercari for the first time or for a foreigner unaccustomed to the Japanese language.

For the first few years following the release of Mercari, most of our users were so-called early adopters familiar with smartphone technology. Right now, our user base has diversified to include everyone from teenagers to senior citizens and foreigners.

That’s why we believe that personalization is the key to creating an app that’s really easy for everyone to use. People should be able to just open up the app and have everything they want laid out and ready to use intuitively on the top screen. That’s what we’re aiming for.

Snehal: I led the redesign of the home screen that was carried out last March, and that aspect of personalization is something I’m keeping in mind, too.

Actually, the last time we tried to redesign the home screen, it was a complete failure. We spent about half a year on it back in 2019. We ended up condensing more than ten categories like “Fashion” and “Sports” into a single tab, but it didn’t turn out very well. Our revisit rate plummeted. Because we had made too many changes, we weren’t even able to figure out which parts our users didn’t like, so we ended up reverting everything back to the way it had been before.

We went back to the drawing board, this time with the idea each and every user has their own individual needs, and took another shot at a redesign centered around personalization. In the end, we released an updated version of the app in March of 2020 that was simpler to use and included elements of personalization under the hood without making significant changes to the look of the home screen.

── Was the second redesign a success?

Snehal: Well, it’s still a long way from perfect, but our data shows there’s been some improvement in usability, so I feel good about the results.

As a user, I was a bit surprised, myself. After the second redesign, I started to see fresh produce being sold by farmers on my home screen. I thought to myself, “Wait, you can buy fresh produce at these prices on Mercari?” It taught me just how powerful recommendations can be for finding bargains.

I want all Mercari users to have experiences like that. Things they aren’t even aware that they want automatically displayed to them; that’s the kind of home screen experience I want to build.

Overseas Expansion is More Than Just Localization

── We’ve been talking about personalization in a more general sense, but there must be a number of ways to go about it. How are you moving forward with your development?

Snehal: Really, the only way to do it is to learn what users like through a process of trial and error.

At Mercari, we have such a diverse group of users that there just isn’t one way to meet all of their needs. So what we do is first implement a new feature, then single out the users with negative responses and attempt to figure out why it is that they dislike it. After that, we implement a tentative solution and see how the users respond. We repeat that process over and over.

Aki: Of course, while data analysis is important, we put a lot of emphasis on user interviews. In the course of these interviews, we find user pain points that would have stayed hidden no matter how long we stared at the data. For example, by listening to our users, we were able to discover that a phenomenon which we had been attributing to an issue with a feature of the app was actually due to the inconvenience of the shipping and packaging process.

── How do you see personalization contributing to the continued growth of Mercari?

Aki: I can see it also being an effective tool in the expansion of Mercari overseas.

When deploying a product to an overseas market, there are two main ways you can go about it. The first is localization. That means surveying the market for each country and optimizing your product for the culture and lifestyles of users in each location: U.S. specifications for the U.S. market, Indian specifications for the Indian market, and so on.

The other is personalization. In other words, skipping optimization for a specific country or culture and jumping straight to optimizing for the individual. By doing it that we, we can make national borders meaningless. While our reach may extend only to Japan and the U.S. at the moment, and we’ve already localized the product to the US market, I believe the precision of our personalization will be an advantage as we continue to expand into other overseas markets.

A System of Development That Accelerates Decision-Making

── With several hundred members, the Product Development Team at Mercari is quite large. How do you go about managing development?

Aki: Since January 2020, we’ve been using a method of agile development called the “Camp System”. We break the product down into multiple areas and set up a “Camp” to cover a set of connected areas.Then, each camp operates autonomously on its development tasks.

We have 3 types of camps: Product Camps, Foundation Camps and Platform Camps. As an example, one of the Product Camps is responsible for things related to registration flow & on-boarding related functions, while one of the Platform Camps is responsible for our microservices architecture.

Before introducing the Camp System, we had been using a “Front-Back System” in which the development of elements the user sees and what happens on the server was done separately. However, this made it difficult for teams to see what others were working on and hampered communication. That resulted in delays in decision-making and development.

That’s where the introduction of the new Camp System came in. In this system, frontend and backend developers, business analysts, UX designers, and other specialized members from a variety of fields make up a single Camp. This way when a problem arises we can discuss it and resolve it within the Camp. It’s reducing communication costs and increasing development speed.

Changes in the tastes and trends of users happen at an incredibly rapid pace. In order to keep up, we need a system that allows us to work quickly.

Snehal: What’s important is that each Camp is capable of making its own decisions autonomously. With the so-called “waterfall model” of management used in most organizations, development requirements are passed down from above and engineers create products according to directives from above.

It’s precisely the opposite with the Mercari Camp System. While we still take company-wide policy into account, each Camp identifies its own challenges and how to handle development on its own. It’s thanks to this system that we are able to make decisions in such a timely manner.

The Best Part of Managing a Superdiverse Organization

── I was surprised to hear that more than half of the engineers at the Tokyo office are of non-Japanese nationality. Given both of your positions in management, what do you think is the secret to managing teams as rich in diversity as those at Mercari?

Snehal: I currently manage teams that include both Japanese and English speakers. So I encourage communication using simple, easy-to-understand English and Japanese to ensure that all members can understand one another.

It then becomes important to listen to the opinions of all members during meetings. It may sound obvious, but even if an idea doesn’t surface right away, it’s important to listen without rushing. I believe that creating a space where everyone feels they can share their opinions is how you get the most out of having such a diverse group.

Aki: You’re absolutely right. On any team there are always going to be those who have no problem sharing their ideas, as well as those who can’t share without being asked, or simply take longer to get their point across. That doesn’t mean it’s okay to disparage the opinions of less vocal members. I believe it’s the role of management to help guide teams in order to facilitate diverse ideas.

── That said, do you ever run into problems where the diversity of opinions and an inability to agree delays decision-making?

Snehal: Actually, it’s quite the opposite. On our Product Development Team, and other teams like it, having a variety of ideas is essential. A piece of functionality that I find trivial may be critical in the eyes of someone from a different culture. If we want people from all over the world to use Mercari, eliciting opinions that differ from our own offers huge hints for achieving that goal.

── What do you think is something unique that you can only get by working on the development team at Mercari?

Aki: Since Mercari is a company with very big ambitions, the executive management team is constantly coming up with new ideas. What’s moreWe have a culture of encouraging employees to challenge themselves, as you might expect from one of the company’s values, “Go Bold.”

So instead of waiting for work to come to them, employees are expected to think and act for themselves. This is true for personalization development as well. Since no one knows the “correct” way to do things, we put our heads together with more experienced members and practice trial and error. It’s not an easy job, but that’s what makes it so interesting.

Snehal: What stands out most in my mind is the final interview I had with Suguru (Mercari CTO Suguru Namura) and Ken (Director of Client Engineering Ken Wakasa) before joining the company.

In a typical interview, you get asked practical things like, “Tell us about your prior work history,” or, “What kinds of development skills do you have?” Those two, however, were straightforward with me about the challenges Mercari was facing, including mentioning the need for a more data-driven approach and a lack of diversity among teams.

Since they were so honest with me, it allowed me to speak frankly about what I would do, too. What makes Mercari special, and a great reason to be excited to work here, is the extremely open attitude toward both the company’s strengths and its weaknesses and the way everyone works together to solve its challenges.

Contributor: Hidenobu Mori
Photographer: Masahiro Kojima
Design: Kirika Kosuzu
Editor: Asuka Kanai

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Production: NewsPicks Brand Design

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