Backend Engineer (Core Banking & Product Features)

Background of Recruitment

We are looking for Backend Engineers to drive the continued growth of the PayPay Group by continuously improving our banking systems and building a robust, flexible next-generation technology platform.

For New Bank Project, we are redefining finance and building a new banking platform through two key initiatives.

Redefining the Financial Experience

The PayPay Group is building a digital financial platform where users can seamlessly access to every aspect of their financial lives-from earning, growing, protecting, and saving money-all within a single app.

As the banking foundation of the PayPay ecosystem, PayPay Bank plays a critical role in enabling every financial service across the platform. By continuously evolving our banking capabilities, we are creating entirely new financial experiences that go beyond the boundaries of traditional banking.

Our ambition is not simply to operate a bank-we are challenging ourselves to redefine what finance can be.

Building an In-House Core Banking System

Today’s banking systems demand greater agility, faster development cycles, higher quality, and better cost efficiency. To meet these challenges, PayPay Bank is building a next-generation core banking system entirely in-house, embracing the same global engineering culture that powers PayPay.

This is an unique opportunity to contribute to one of the largest core banking modernization projects in the financial industry. You’ll help design and build the technology platform that supports one of Japan’s largest digital user bases while shaping the future of banking from the ground up.

To drive transformation at PayPay’s exceptional speed, we are looking for engineers who are adaptable, proactive, and eager to take ownership beyond defined roles and responsibilities. We value people who create opportunities for themselves, embrace challenges, and turn ideas into impact.

Rather than being attached to a particular programming language or technology, we view technology as a means to solve meaningful problems. You will collaborate with your team to maximize product impact and business value, always putting the user first.

If you’re passionate about building products with a user-first mindset and helping redefine the future of finance, this is an opportunity for you.

※ After joining the company, you are expected to be seconded to PayPay Bank as a member of the above project.

Tech Stack

We select the best combination of tech at times.

• Spring Boot, JUnit, Resilience4j, Feign
• MySQL/AuoraDB, DynamoDB, ELK, Kafka, Redis
• Docker, Kubernetes, ArgoCD, AWS
• GitHub, Gradle, Maven, npm/yarn, Flyway
• PlantUML, draw.io, miro.com
• Slack, Zoom, Confluence, Jira

Attractiveness of This Position

• Gain experience from the design to the introduction of a new system renewal
• Opportunity to collaboratively build a new organization and environment
• Acquire high-level planning and proposal capabilities through supporting top management’s decision-making and high-level coordination with various departments and affiliated companies, including PayPay
• Gain frontline work experience in the industry at a company aiming to provide unprecedented financial services during a transformative period in the financial industry
• Ability to leverage PayPay’s service and user base

Project Examples

• 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.

Responsibilities

• Develop and operate backend applications in Java language (Java/Kotlin) 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

Requirements

• 3-5 years of backend development experience
• Practical experience in 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
• English (Business level conversational proficiency)
• Hands-on experience with AI/LLM tools (e.g., ChatGPT, GitHub Copilot, Gemini, CodeWhisperer, or similar) in professional software development.

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
• Experience with microservices
• Ability to conduct business in Japanese (native-level proficiency or equivalent to JLPT N1/N2)
• Proven track record of integrating AI-assisted development into system design and delivery
• Contributions to AI-related open-source projects or automation of workflows with AI is a plus