about Tech Talks
In this Tech Talks series, we share the everyday life of the PayPay Product team through the eyes of members from over 35 countries around the world. This time, Julien from the DevSecOps team will share his story.
* Japanese version of article is also available.

Julien Kasarherou
I have Joined PayPay in March 2020, and am currently with the DevSecOps team.
What I’m working on currently:
Our mission, as DevSecOps, is to constantly improve the reliability and the security of the PayPay platform.
The DevSecOps Team:
Here are what we do at the DevSecOps team.
- We are deploying our services to new data centers, so we create new network infrastructure and Kubernetes clusters using AWS cloud services.
- Create and deploy tools to improve the monitoring and reliability of our Kafka clusters.
- Check and make sure that our AWS infrastructure configuration is following security best practices.

A Technical Challenge I Experienced Recently:
One technical challenge I had was to debug a strange error we experienced in one of our internal proxy services. During high traffic, we experienced degraded performance of some of our API endpoints, and it seemed like the request distribution among Kubernetes pods was really unbalanced. After multiple days of investigation, I found the root cause, which was due to a combination of a sticky session setting and a buggy version of our internal proxy component. I shared my findings with the team and presented a plan to roll out the new improved setting and version in our production services. It was very satisfying to have successfully fixed the issue, and in the process, I learned a lot about our internal systems.
What I like to Challenge at PayPay:
Because PayPay is expanding and becoming a more mature organization, I want to share my knowledge and experience to newcomers in the company when onboarding.
My Typical Daily & Weekly Schedules:
Every morning, we have a daily online standup meeting with the team. It is an opportunity to share your work progress with everyone and also catch up on the latest updates. During the rest of the day, we mostly use Slack to communicate, which I think is a great tool for productivity.
- 09:00
- Start work
- 10:30
- Daily standup meeting (20 min)
- 12:00
- Lunch break (1 hour)
- 16:00
- One-on-one meeting to discuss weekly progress and miscellaneous topics
- 18:00
- End of the day
Note: We don’t have too many meetings, so we can focus on our work.
My Career Before Joining PayPay:
Before joining PayPay, I was working for a small startup that I co-founded which specialized in cloud storage infrastructure software.
After my company got acquired in 2020, I wanted to join a different sector of the IT industry. I was really interested in FinTech because of the big growth in cashless payment systems in Japan.
Getting to work with people of multiple backgrounds and cultures is really an invaluable experience. I really enjoy learning new things daily, and also being able to share and discuss ideas with my teammates.
The Reason I Decided to Join PayPay:
I found out about PayPay first as a regular app user, and I wanted to know more about the kind of infrastructure that can handle such high scale user traffic. One important point for me was that the PayPay organization was very diverse and had many non-Japanese members, so I felt more confident in joining the company.
It seemed clear to me that PayPay was the leader in the mobile cashless domain in Japan, so I was excited to join the PayPay team to help build and improve the payment system.
A Message to Aspiring PayPay Employees:
At PayPay, we work completely remotely. I must say it has been challenging to adapt, but this work style brings a lot of advantages, for instance, flexibility to plan your schedule outside of work.
Something I like with PayPay, is that there’s a lot of different and interesting subjects to work on. Also, if we want to improve some aspect of our work, we are strongly encouraged to bring in new ideas and implement them ourselves.
For example, I wanted to introduce new ARM based instances in our infrastructure, so I made a POC, presented the results to the team, and now it is being used in the production environment.
I had to quickly discover and learn so many new things in the first month. If you like learning and using new technologies you will like working here.
Currently available positions
Author: Julien / Editorial Supervisor: Mune / Managing Editor: Az
* Employees’ affiliations are those of the time of the interview.