Backend Engineer (PayPay Card)

About PayPay CardPayPay is a FinTech company that in the six years since its launch in 2018, has surpassed 70 million users (as of July 2025) and is rapidly expanding its business scale as a payment platform used by approximately one in two smartphone users in Japan.PayPay Card was established in 2021 to provide users with more accessible and convenient FinTech services that were previously not possible with credit cards and credit services by integrating with the PayPay payment platform. We are looking for professionals who are passionate about refining our products at an overwhelming speed that no other company can match, and promoting the spread of cashless payments in Japan and the financial life platform that uses them. We are looking for people who are passionate about this.We are looking for backend engineers to build, or rebuild, rock solid services with a laser focus on scalability and maintainability.PayPay Card aims at revolutionizing the credit card industry, making payment easier than ever, from two different angles:Bring the credit card experience to the next level: we have many functionalities in the pipe to improve our product, not to mention the integration into the PayPay ecosystem as PayPay Card is part of the PayPay Group.(Re-)architect our systems landscape: we want to reassess and fix the behind-the-scenes to power a top-notch user experience. It is bundled with difficult design challenges to solve: we simply want to get it right.As a fast-paced company leading the payments industry, we need our engineers to be versatile and enthusiastic to take on new challenges in order to stay at the forefront. Indeed, we strive for continuous improvement within our systems as well as outside our systems. Additionally, we value communication, to smoothly cooperate with other teams, and inclusivity, to efficiently navigate in a multicultural environment.Main ResponsibilitiesSupport the design, implementation and delivery of large scale, and complex, systems, while collaborating with product managers, frontend engineers or other team members.Understand how to leverage infrastructure to solve large scale problems.Contribute to the team by sharing knowledge, participating in code reviews and providing feedback to uphold and ensure best practices.Triage, debug and resolve product issues or other incoming troubles inquiriesAdopt problem solving as a way of life – always go to the root cause! Support the code you write in production.Tech StackWe currently work withBack-end services:・Main implementations are in Spring Boot, with a mix of Java 11/Spring Boot 2 and Java 17/Spring Boot 3.・Some legacy systems are written in Java EE.・Testing is done with JUnit and Mockito・Deployment relies on AWS ECS・CI/CD is handled by AWS CodePipelineInfrastructure・All our services run in AWS・Infrastructure is managed by AWS CloudFormation・AWS CloudWatch is used for observabilityCoding environment: GitHub, IntelliJ, GradleDocumentation & Project management: Confluence, Miro, JIRACommunication: Slack, Zoom, Office 365Please note that PayPay Card is challenging its current architecture, potentially introducing new technologies and/or deprecating existing ones.QualificationsExperience in using Spring Boot in a professional environment.Experience with RDBMS, NoSQL databases along with distributed cache.Strong fundamentals in data structures, algorithms and object oriented programming.In-depth understanding of concurrency and distributed computing.Degree in Computer Engineering or Computer Science or 5+ years equivalent experience in SaaS platform development.English business proficiencyPreferred QualificationsExperience with implementing platform components such as RESTful APIs, Pub/Sub Systems, Database Clients.Experience in system design for high traffic application with scalability in mindExperience in microservices & event-driven architectureExperience in a multicultural environmentJapanese conversational proficiency is a plus