Tech Talks vol.29 – Backend Engineer

About Tech Talks

In this Tech Talks series, we will share with you the attitude and vibe of the PayPay Tech Team through the voices of the unique product members from around 50 countries!
In today’s chat, we spoke with Takayuki Inoue, Tech Lead on the Bank Team.

What made you decide to come to PayPay?

In my search for a company in which I could help develop a B2C system with a high transaction volume, I was attracted to the chance PayPay presented to get involved in the development of large-scale systems in the area of payments, which demands high availability. During my interview, I was told the work is done fast with a lot of discretion, making it an attractive environment for an engineer. I decided to join since PayPay’s startup-like and challenging environment was exactly what I was looking for.
I was also drawn to the diversity here, which enables me to meet engineers of various nationalities.

What do your career and responsibilities at PayPay look like?

For my first two and a half years after joining, I was responsible for the development and operation of new microservices that handle external connections as a backend engineer on the Finnet & KYC Team. I became a Subteam Lead after about a year here, then a Tech Lead when I transferred to the Bank Team, which was newly established in April 2023.

Not counting my internship, PayPay is my first job as an engineer. This made me worried at first, but since we are entrusted with so many things here, I’ve been able to ― with the help of my teammates ― keep up and make it through to today.

Now, I’ve stepped up to the plate as a Tech Lead responsible for running my team, undertaking team management tasks like code reviews and assignment management ― not just designing new features for development.

What project stood out the most to you?

The first project I developed as a Tech Owner after a year with the company, the Second Myna Points Project, which is a government initiative including a PayPay collaboration awarding points to Japan residents who apply for a “My Number,” or Individual Number Card. When I was an individual contributor I only had to consider my own components, but becoming a Tech Owner forced me to think about projects from end to end and work closely with other teams and third parties.

In particular, the Myna Points Project required us to process a huge number of transactions in a point-granting batch, so I kept performance in mind as I did my designing and coding.
The moment we released the project, we really did see a huge flood of transactions all at once. Monitoring it all in real time was a very moving experience for me!

What’s the biggest challenge you have faced at PayPay?

I often create components that handle external connections, and I always find it challenging to integrate seamlessly with external APIs.
Other companies’ systems do not work the way we want them to, and in some cases the interfaces come with complexity or there are capacity issues. There are many points to check, such as whether they meet PayPay’s security requirements, because their authentication and authorization mechanisms are all different.

Therefore, we do not rely solely on documents, but also prioritize direct and thorough discussions to confirm details. And instead of designing projects around a third-party system, we start with what we at PayPay want to achieve, then think of how the third party can fit into that.

How have you grown most since joining PayPay?

In my understanding of and skill in system design.
When designing a system we need to clearly understand its characteristics, and based on that think about and document the data models, what APIs to use, and how to handle errors before we can move on to the coding process.
To be honest, I thought that having coding skills was good enough when I first joined, but I’ve come to the keen realization that design is crucial.

What is the allure of working as an engineer at PayPay?

The best part is that it is chaotic in a good way. With new requirements arising every day, our team enjoys coming together for things like architecture reviews, and the sense of excitement and fun in those processes is very rewarding. I can’t get enough of the feeling that we are all chipping in to make something big!

The second is our diversity. Our environment is quite stimulating in that we can exchange opinions with engineers from all over the world. There is a sense of openness that enables engineers to discuss and act on any room for improvement they might see.

The third is the point that drew me to PayPay in my job hunt ― the opportunity to challenge yourself. It is rare to find a company that operates microservices at such large scale as a single application, and I’ve personally grown from having to provide the high availability needed to keep up with our lightning-fast business speed and growth.

And fourthly would be working from home. The lack of commute gives me more time for myself, say, taking a walk with my wife or cooking dinner. Sometimes I even get away from Tokyo for a week or so for a change of pace.

What do you want to try out next at PayPay?

My goal is to be able to design applications for the general public from scratch, so I want to hone my skills through taking on more and more critical projects. I would especially like to be involved in the development of systems that have to handle high levels of traffic.

At the same time, I would like to improve my team management skills, which is one challenging area for me. I hope to learn how to visualize tasks, and also draw out team members’ opinions to improve our products so that our team can maintain its maximum potential.
I would also like to work on improving the review process, sharing design documentation, and building coding standards.

Finally, any words for job seekers?

PayPay is a service with a large number of transactions, which means what you create will be delivered to a large number of people and make an impact on the world. With a great deal of discretion and many opportunities to be involved in design even as a junior, this is a great place to be if you want to grow. Our systems demand complex requirements and scalability to boot, making it ideal for those who enjoy a challenging environment.
If you can propose and act on your own ideas without becoming passive, I think you will be successful here!

*Recruitment status and employee affiliations are correct at the time of the interview.