Keynote

How to Unleash Fintech

Listen in on a three-person panel discussion between our CTO and VPoEs. In this session, two of our VPoEs will take a deep dive on the Keynote speech to cover the future of Fintech business at Mercari Group and talk about where they would like to put their focus going forward. In looking at their desired focus areas, they will speak openly from both the perspective of the product and the organization about the issues they are wrestling with and current initiatives, as well as future initiatives they would like to implement.

Developments Since Launching Operation of Android Automated Testing to Support One-Week Releases

In order for the Merpay Android Team to support the operation of weekly releases, they have been working on an initiative to automate regression testing carried out prior to making judgement about whether to make a release. In the past, the team also published an article that covered test automation, but after the redesign of the Mercari marketplace app, the structure of the organization changed extensively, and the test system has also changed over the past year and a half.
This session covers how the Merpay Android Team has worked on automated testing.

Migrating Merpay to the GroundUp App on iOS

Toward the end of 2022, the Mercari marketplace app for iOS went through large-scale re-architecturing and was reborn as an app based on SwiftUI.* However, due to business requirements, the grouping of Merpay features had to be transferred as is from a UIKit-based code to a SwiftUI-based app.
In this session, we’ll describe the strategy we used to complete the transfer without any significant incidents and further explain the subsequent overall work performed to migrate to SwiftUI.
*  https://engineering.mercari.com/blog/entry/20221213-ground-up-app/

Swift Concurrency Support for Merpay for iOS: Frustration and Where to Go From Here

From last year to the beginning of 2023, the Merpay iOS team worked on Swift concurrency handling. The project involved changing build options and applying concurrency checks with a compiler in order to support Swift 6. In doing this, we gained a variety of knowledge about Swift concurrency, but in the end we were unable to release a version that supported concurrency.
In this session, we explain the nature of the concurrency handling that we did, the reasons why we decided to stop the project, and our projections going forward.

Improving and Re-implementing the Bitcoin Price Chart Using SwiftUI

The Mercoin iOS Team works on development for Mercari’s bitcoin transaction feature. At Mercoin, we implement a large portion of our work using SwiftUI, but we implemented the bitcoin price chart in UIKit using a library. However, because there are limitations imposed on the library and because we were unable to create all of the expressions that we wanted to create as a team, in the end we reimplemented the feature using SwiftUI and sped up the improvement cycle.
In this session, we talk about a number of topics such as the implementation of the chart using SwiftUI and how we improved the cycle to make it high speed.

Improving the Skill Test Evaluation System of Our Frontend Team

One part of the hiring process for Merpay’s Frontend Team is a skill test. Without a formal evaluation method, the process has relied heavily on the evaluation skills of individuals, making stable and consistent evaluation difficult. In order to fix issues like this, the team spent a long time developing an evaluation rubric and method.
In this session, we’ll share our efforts to ensure stable and consistent evaluation of skill tests.

Behind the Scenes: The Technical Magic that Powers our WYSIWYG Webpage Builder

We will share our journey on how we built a WYSIWYG Webpage Builder, from concept to launch.
With a flexible component system and conditional rendering functionality, our WYSIWYG page builder streamlined workflows, eliminated the need for coding and technical skills to create beautiful and responsive webpages, and allowed our company to create 150% more webpages than without it. We will describe our practices for building a WYSIWYG page builder, such as finding a balance between versatility and complexity. Attendees will leave with a deeper understanding of how to leverage shared knowledge to create an efficient and effective page builder.

Preventing Fraud in the Mercari customer journey

When a person wants to use the Mercari app, they go through multiple phases over the course of their customer journey, from registering their account to liking, buying, and selling items and more. During these phases, we must take the utmost care in handling customer actions because there is a risk of fraud.
In this session, I will discuss a few architecture details and design discussions that we took to prevent fraud in the Mercari/Merpay ecosystem.

Customer Identity Verification in Japan and Incoming Technical Challenges

Merpay’s KYC Team is dedicated to customer identity verification topics, enforcing compliance of our system to be aligned with the latest law and regulation updates in order to keep Mercari’s services safe for our users.
Regulations specific to online KYC (eKYC) have been introduced, and Japan’s online system is operating mostly smoothly so far. However, with the recent legislation changes around the My Number Card, and discussions beginning about innovative technologies such as Deepfake, the online identity verification landscape may change significantly in the future.
In this talk, Mann, Chris, and Tim from the KYC Team will discuss the history of identity verification in Japan, its most recent evolution, and the potential incoming challenges that Japan might have to face in the future.

How FIDO was Implemented in Mercari, What the Future Holds, and the Lessons We’ve Learned From the Challenges We’ve Faced

We implemented FIDO and passkeys within Mercari for the first time with Mercoin, a service with high security requirements. In this session, we will give an overview of FIDO implementation. In our main discussion, we’ll also cover the issues that the engineers who actually worked on implementation confronted and examine their feedback. Participants who have basic knowledge of FIDO can expect to get more out of this session.

The Development of the Repayment Platform Microservices Supporting Merpay deferred payments and Smart Money

Together with the release of Merpay Smart Money, our engineers created a microservice that provides repayment features, including such things as invoices for existing deferred payments. At the time the product was released, there was a divide between the configuration of the microservices and the ideal responsibilities of each microservice, but in the process of splitting microservices and implementing data migration, it has become closer to the ideal architecture.
In this session, we’ll share the story of how we developed the architecture of our repayment platform microservices by tracing a line from the early days of development to the present.

Designing Softwares for Extensibility

Providing solutions to our marketers has been a unique problem, where we have the advantage of having internal customers. However, the requirements are never frozen (and that's always for a good reason). With this, we took the challenge to build a product that can still serve the business while it's being built.
This session tries to cover the challenges we saw and the options we took to build our Engagement Platform. It also covers how product development is different from solution development, and how to strike a balance between extensibility and speed. We will look at examples of a few major use cases while we discuss this.

Behind the growth strategy that bolstered the issuing of 1 million Mercards

Mercard, which was launched last year, recently reached 1 million cards issued. Behind the scenes, we have carried out a variety of growth initiatives, including the development of new product features and UX improvements, as well as the development of campaigns and other growth-oriented activities.
In this session, we will discuss how PMs (Product Managers) and engineers have worked together to develop these things in parallel, and how engineers have worked on development while keeping business goals in mind.

Behind the Development of Mercard’s Point-Back Rewards System

In this session, we will talk about the backend mechanisms behind Mercard's point-back rewards system, the position of the growth infrastructure in the microservice architecture, and design decisions made during development, including background information.

The Mechanisms Behind Merpay Merchant Sales Processing

In this session, we’ll talk about a number of topics including such things as the mechanism behind sales processing at Merpay merchants, as well as the issues that our engineers have confronted in their work and the future direction for the development of the microservice architecture.

Using Go to Implement SQL Query Tests

The team charged with developing a management system for Merpay merchants deals with SQL queries for BigQuery that have a number of complex requirements. For instance, for calculation queries for such things as calculating costs related to merchant management, the requirements change periodically due to changes in the external environment. As a result, there are some queries for which it is difficult to systemize operations using such things as microservices. The complexity of these kinds of queries has not been the only difficulty we have encountered, either; there were also issues with testability. This made it cumbersome for developers to test their work and did not allow them to feel completely at ease with the query changes that they made.
In this session, we’ll talk about our initiative to create automatic tests as Go test code for working with SQL queries for BigQuery that have a number of complex requirements.

Accelerating Fraud Detection Using Data on Fraud Risk of Potential Transactions

In this session, we will introduce a new mechanism for faster fraud detection.
Fraud detection using batch inference carries the risk that fraudulent activities may conclude before the machine learning model detects them, resulting in response delays. Therefore, in this session, we will present a mechanism that calculates fraud risk using attribute data of potential transactions. By combining near-real-time feature data and an risk inference platform, we will recalculate the risk every time the attribute data is updated. This enables the detection of fraudulent activities before they occur.

Quality Assurance and Risk Management in Merpay ML

Merpay is the first company to obtain certification as Comprehensive Credit Purchase Intermediary in Japan, enabling it to calculate a user's spending limit based on its own data through machine learning, rather than relying on fixed information such as income. However, this also means that, compared to traditional financial institutions, quality assurance and risk management are even more critical for managing the errors generated by AI and the supporting systems. To accomplish this, governance through articulated rules is essential, not just raising the awareness level of engineers working directly on the product.
In this session, Merpay's Machine Learning Team will discuss how they are systematizing risk management from both system and model risk perspectives.

Leveraging LLM at Merpay & Mercoin

At Merpay and Mercoin, we have established a new team that aims to leverage LLM and generative AI to enhance our services and improve productivity.
In this session, the members involved in establishing the team will use a panel discussion format and make presentations to talk in detail about what shape their efforts are taking, to share information on individual use cases, and to touch on the issues they have seen in their activities and expected future developments.

Creating an Internal Service for Monitoring BigQuery Data

The Merpay Data Management Team builds and supports mechanisms and processes that allow users of internal data to leverage our information assets safely, securely, and easily. At some point, the team began receiving individual requests from several teams that use data in their work. The requesters wanted to receive Slack notifications when BigQuery data was not correct. However, at the time there was no internal service that monitored data based on requirements like these. In response, the team developed and launched a system as an internal service for monitoring BigQuery data internally that made notifications like the ones requested accessible not just to the team that made the request, but also to other teams that wanted to receive notifications in the future.
This session will talk about how the team configured the system of the service.

Creating Security Guidelines for the Internal Use of GitHub Actions

In tandem with the expanding use of GitHub Actions at the company, we believed we should have guidelines for using this form of automation safely and securely.
This prompted us to have volunteers within the company write our GitHub Action Security Guidelines, and we managed to formulate these guidelines by following a peer review process that involved our internal Security Team and an assortment of other members.
While the guidelines were intended for internal use, we saw that they could also be beneficial to people outside of the company as well and decided to publish them on our engineering blog, which received a mountain of responses.
In this presentation, we would like to share a portion of the guidelines with you, showcase how we use them internally, and also present to you the process we used to create the guidelines.

Initiatives Involving BigQuery Computing Resource Management

Mercari Group uses BigQuery as our data analysis infrastructure. It allows us to use SQL queries to easily describe the analysis process for large amounts of data, and because it executes quickly, many users at the company leverage it conveniently. On the other hand, precisely because it is convenient, our resources are pushed to their limits, and at times problems emerge such as decreased performance and jobs timing out.
In this session, we’ll talk about the issues we confronted involving BigQuery computing resource management and the initiatives we took to resolve them.

The “Fake Clock” Microservice: How to Hack the Time for Testing

For Merpay deferred payments and Merpay Smart Money, there are cases where our engineers wanted to use invoices that were two months overdue in tests.
Since running tests in real time over a period of two months was too inefficient, the team created a hack that allows them to complete tests in a shorter amount of time by using a mechanism called fake clock.
In this session, the developers discuss the issues they encountered when a test straddled multiple microservices and how they resolved this.

SRE Initiatives to Design and Construct Mercoin’s Infrastructure and Release Reliable Services

In tandem with the service launch of Mercoin, SRE designed the infrastructure for Mercoin, building it in a limited amount of time and also managing to work with backend engineers to create dozens of microservices and get the service production-ready for what was ultimately a safe launch.

Communication Architecture for Implementing Data Separation Between Systems at Mercoin

When dealing with Mercoin, from the perspective of protecting data privacy, Mercoin uses different user IDs than Mercari or Merpay. At the same time, Mercoin’s system depends on Mercari and Merpay’s systems, and it’s necessary to specify the user in order to communicate between the different systems.
In this session, we’ll talk about how we designed the system architecture for communicating between systems amid these restrictions.

Building a Global environment at Merpay: India & Japan

Merpay is being developed by diverse talents from over 40 countries.
Last year, Mercari established the Center of Excellence in India, and Merpay now has development teams not only in Japan, but also in India.
Join us to find out how we work together, what we learned, and what our future looks like!

Standardizing Test Case Formats to Enable Seamless Fintech QA

In order to provide our users with better services as fast as possible, the Merpay QA Team works to improve the productivity of our day-to-day quality assurance activities. Our initiative to standardize test case formats is one such recent example. In this presentation, we will relate how the QA Team created the test case format that all of our members use, as well as share things like processes ranging from planning and decision-making to starting operations and the issues we discovered in the process of operations.

Implementing the Mercoin Payment Platform

In order to support Mercoin’s cryptoasset business, our members leveraged their development experience of working on the existing Merpay payment platform to redesign and develop the Mercoin payment platform.
In this session, we’ll share the configuration of the Mercoin payment platform and each domain component and explain the relevant technical development points in detail.

The Technology Supporting Transaction Management for Mercoin’s Payment Microservices

At Mercoin, operations related to increasing or decreasing a user’s balance are executed via payment microservices. For these microservices, the features for guaranteeing consistency and for reconciliation are very important. This session will describe in detail the technology used to implement this feature.

Merpay Engineering Career Talk

In this presentation, three of our members who joined Mercari Group as mid-career software engineers will each talk about their career path. Regardless of whether you work for Mercari Group or another company, the business environment for engineers is undergoing significant changes. In that context, we would like to deliver some of the realities of conflict and decisions people face as each and every company employee interprets the turning points of their career.
In a panel discussion format, this session will answer questions received from participants watching online, so please join us.

Testing the Re-Architecture on Giant BFF Services That Use gRPC Federation

Merpay operates using a backend service that collects and returns the results of calling multiple microservices in response to requests from the application. More than four years after the release of Merpay, amid dependencies on multiple microservices and a ballooning codebase, questions arose about which team is responsible for this service and about who was responsible for absorbing maintenance costs for operating this service. To address this and clarify which teams were responsible for the service, we came up with a plan to divide the ballooning service into multiple services. This session will talk about how we are considering developing and implementing a mechanism called gRPC Federation, which can build a federated architecture that targets gRPC protocols to keep maintenance costs from becoming too high.

My Experiences as Engineering Head of the Enabling Program

In 2023, Merpay implemented a program system as our development structure. The “Enabling Program” is a cross-functional team that provides development support for other programs. I’ll take a look back on how we used to do things before the start of the program and talk about what’s changed since. As the Engineering Head of the Enabling Program, I’ll also talk about the direction of the program.