Backend Engineer (New Bank Project)

**About the company:** PayPay Minato-ku, Tokyo With over 70M million registered users (as of July 2025), PayPay is the country’s most popular mobile wallet used by approximately one out of every two smartphone users in Japan. **Responsibilities:** Develop and operate backend applications in C and Java for core banking systems Designing and developing for both performance and stability to maintain high reliability as a financial platform Understanding and implementing how to utilize infrastructure to solve system challenges Designing architecture based on application requirements and selecting middleware, etc. Performance tuning, monitoring settings, and alert response for microservices Example projects include application development for new services and improvements to existing services: Account opening linked with LINE, inquiry chat PayPay mini-app integration Expansion of cardless ATM usage Improvement of account opening processes Improvement of various loan services, etc. Requirements 3-5 years of backend development experience Practical experience in C or Java. Excellent skills in other common programming languages Understanding of data structures, algorithms, and the basics of object-oriented programming Schema design in DB (RDB, NoSQL, etc.) and efficient query creation Experience in web application development and tuning, and development with security considerations Japanese (Native or equivalent to JLPT N1 or N2 proficiency) Nice to haves While not specifically required, tell us if you have any of the following. Development experience in the financial industry Experience implementing platform components such as RESTful API, Pub/Sub systems, database clients Development experience using AWS services Experience in system design, developing applications/web products handling large transactions, and applications/web products requiring scalability Development experience in both C and Java Experience with microservices English (Business level conversational proficiency) APPLY FOR THIS POSITION DO YOU NEED MORE INFO? ASK A QUESTION Meet PayPay's Developers Growing your career by asking for you want with Ashwini Meshram Ashwini leads one of PayPay’s payment sub-teams. She got there by doing something she’s done throughout her career: identifying something she wants to do and asking to do it. Read their story... Refactoring PayPay’s Android App with Adrian Mariadas Adrian came to Japan to join PayPay as an Android Engineer. As the app has grown in scope, refactoring the codebase to ensure development can continue at a rapid pace has been a big part of his job. Read their story... iOS Development at PayPay with Yoseph Savianto Yoseph joined PayPay after being attracted to their mission of making Japan a cashless society. As an iOS Engineer, he originally joined their iOS feature team, but now works on their platform team, creating an internal SDK for their iOS and Android apps. Read their story... Rapidly scaling to tens of millions of users with Shilei Long Shilei started working on PayPay before it launched, and has seen it grow into a product used by tens of millions of users. He explains how diversity has helped them overcome challenges, and what PayPay is looking for in candidates. Read their story... **Requirements:** 3-5 years of backend development experience Practical experience in C or Java. Excellent skills in other common programming languages Understanding of data structures, algorithms, and the basics of object-oriented programming Schema design in DB (RDB, NoSQL, etc.) and efficient query creation Experience in web application development and tuning, and development with security considerations Japanese (Native or equivalent to JLPT N1 or N2 proficiency) **Nice to have:** While not specifically required, tell us if you have any of the following. Development experience in the financial industry Experience implementing platform components such as RESTful API, Pub/Sub systems, database clients Development experience using AWS services Experience in system design, developing applications/web products handling large transactions, and applications/web products requiring scalability Development experience in both C and Java Experience with microservices English (Business level conversational proficiency) APPLY FOR THIS POSITION DO YOU NEED MORE INFO? ASK A QUESTION Meet PayPay's Developers Growing your career by asking for you want with Ashwini Meshram Ashwini leads one of PayPay’s payment sub-teams. She got there by doing something she’s done throughout her career: identifying something she wants to do and asking to do it. Read their story... Refactoring PayPay’s Android App with Adrian Mariadas Adrian came to Japan to join PayPay as an Android Engineer. As the app has grown in scope, refactoring the codebase to ensure development can continue at a rapid pace has been a big part of his job. Read their story... iOS Development at PayPay with Yoseph Savianto Yoseph joined PayPay after being attracted to their mission of making Japan a cashless society. As an iOS Engineer, he originally joined their iOS feature team, but now works on their platform team, creating an internal SDK for their iOS and Android apps. Read their story... Rapidly scaling to tens of millions of users with Shilei Long Shilei started working on PayPay before it launched, and has seen it grow into a product used by tens of millions of users. He explains how diversity has helped them overcome challenges, and what PayPay is looking for in candidates. Read their story...