Backend Engineer

About the role

PayPay is seeking a Backend Engineer to join our engineering team and contribute to the development and enhancement of our payment systems. This role involves designing, building, and maintaining scalable backend solutions that support high-volume transactions and ensure a payment experience for users. The ideal candidate will work closely with cross-functional teams to implement features, optimize system performance, and incorporate innovative technologies such as AI and large language models (LLMs) into our workflows. As part of our team, you will play a vital role in advancing our FinTech platform, ensuring security, reliability, and efficiency in our services.

Key facts

What you'll do

• Design, develop, and maintain large-scale backend systems capable of supporting high transaction volumes and ensuring system stability.
• Collaborate with product managers, frontend engineers, and other stakeholders to translate business requirements into technical solutions.
• Optimize infrastructure to handle large-scale challenges, including performance tuning, capacity planning, and scalability improvements.
• Develop tools and automation scripts to streamline deployment, monitoring, and incident response processes.
• Contribute to open source projects when relevant, sharing knowledge and best practices with the broader developer community.
• Implement security measures to protect sensitive payment data and ensure compliance with industry standards.
• Incorporate AI and LLM-based tools such as ChatGPT or GitHub Copilot into daily development, testing, and documentation workflows to improve productivity and code quality.
• Conduct code reviews, write unit and integration tests, and participate in continuous integration and deployment (CI/CD) pipelines.
• Stay updated with emerging technologies, industry trends, and best practices to continuously improve system architecture and development processes.
• Troubleshoot and resolve system issues promptly, performing root cause analysis and implementing long-term solutions.
• Document system designs, APIs, and operational procedures to facilitate team collaboration and knowledge sharing.
• Support the onboarding and mentoring of junior engineers, fostering a collaborative and innovative team environment.
• Ensure that the backend systems adhere to company standards for quality, security, and performance.

Requirements

• Minimum of 4 years of professional experience with Java, or strong proficiency in other programming languages such as Scala, Python, or Go.
• Willingness and ability to learn new programming languages and technologies as needed to meet project requirements.
• Experience working with NoSQL databases, such as DynamoDB, and distributed caching solutions like Redis.
• Solid understanding of data structures, algorithms, and object-oriented programming principles.
• Knowledge of concurrency, distributed computing, and system scalability concepts.
• A degree in Computer Engineering, Computer Science, or related field, or at least 5 years of equivalent experience in SaaS development.
• Proficiency in English or Japanese at a business level to facilitate communication within the team and with stakeholders.
• Practical experience using AI/LLM tools such as ChatGPT or GitHub Copilot in a professional setting, demonstrating familiarity with AI-assisted development workflows.
• Ability to work effectively in a team environment, communicate technical concepts clearly, and adapt to changing priorities.
• Strong problem-solving skills and a proactive attitude toward identifying and resolving system issues.
• Experience with RESTful API development, microservices architecture, and cloud platforms is a plus but not mandatory.

Nice to have

• Experience in building platform components such as RESTful APIs, Pub/Sub systems, or message queues.
• Familiarity with AWS cloud services, including EC2, S3, Lambda, and others.
• Background in finance, payment processing, or related industries, providing domain-specific knowledge.
• Experience designing scalable web systems capable of handling high transaction volumes efficiently.
• Bilingual proficiency in Japanese and English, facilitating communication across diverse teams.
• Knowledge of microservices architecture, containerization, and orchestration tools like Docker and Kubernetes.
• Demonstrated success in integrating AI tools into development workflows, automating tasks, or enhancing system capabilities.
• Contributions to open-source projects related to AI, cloud computing, or backend development.

Skills & tools

• Programming languages: Java, Kotlin, Scala, Python, Go
• Frameworks and libraries: Spring Boot, JUnit, Resilience4j, Feign
• Databases: MySQL/AuroraDB, DynamoDB, ELK, Kafka, Redis, TiDB
• Containerization and orchestration: Docker, Kubernetes, ArgoCD
• Cloud platforms: AWS, GCP
• Version control and CI/CD: GitHub, Jenkins, Flyway, Snyk, IntelliJ, Gradle, Maven, npm/yarn
• Data analytics and processing: BigQuery, Kibana, Spark
• Diagramming and collaboration tools: PlantUML, draw.io, miro.com
• Communication tools: Slack, Zoom

Practical notes

• Visa sponsorship and relocation assistance are available for qualified candidates, supporting international applicants to join the team.
• PayPay offers a flexible work environment, promoting work-life balance and employee well-being.
• The company provides comprehensive benefits, including social insurance and a 401K plan, to support employees' financial security.
• Applications must be submitted individually; multiple applications for different positions within PayPay are not permitted.
• Candidates are encouraged to demonstrate their experience with AI/LLM tools and how they have integrated these into their development workflows.
• The role involves working on-site at our hybrid location, with expectations for regular presence at the office.