Backend Engineer

About Pay Pay

Pay Pay is a Fin Tech company that has grown to over 70M (as of July 2025) users since its launch in 2018. Our team is hugely diverse with members from over 50 different countries.

OUR VISION IS UNLIMITED_

We dare to believe that we do not need a clear vision to create a future beyond our imagination. Pay Pay will always stay true to our roots and realize a vision (future) that no one else can imagine by constantly taking risks and challenging ourselves. With this mindset, you will be presented with new and exciting opportunities on a daily basis and have the opportunity to grow and reach new dimensions that you could never have imagined.

We are looking for people who can embrace this challenge, refresh the product at breakneck speed and promote Pay Pay with professionalism and passion.

Please note that you cannot apply or be selected in parallel with Pay Pay Corporation, Pay Pay Card Corporation and Pay Pay Securities Corporation.

Pay Pay is looking for a Backend Engineer to work on our payment system to deliver the best payment experience for our customers.

At Pay Pay, we believe that the future of software development is AI-augmented. Every engineer is expected to actively leverage AI tools for code reviews, testing, documentation, debugging, and productivity. AI is not optional – it is a mandatory part of our daily engineering workflow. Candidates must demonstrate both experience and mindset in utilizing AI effectively to deliver high-quality systems faster and better.

• Design large-scale systems with high complexity to support our high throughput applications.
• Understand how to leverage infrastructure for solving such large-scale problems.
• Develop tools and contribute to open source wherever possible.
• Adopt problem solving as a way of life – always go to root cause! Support the code you write in production.
• Leverage AI/LLM-based tools for code development, reviews, testing, and documentation in daily workflows.

• Java, Kotlin, Scala
• Spring Boot, JUnit, Resilience4j, Feign
• MySQL/AuroraDB, DynamoDB, ELK, Kafka, Redis, TiDB
• Docker, Kubernetes, ArgoCD, AWS, GCP
• Git Hub, IntelliJ, Gradle, Maven, npm/yarn, Flyway, Jenkins, snyk
• Bigquery, Kibana, Spark
• PlantUML, draw.io,
• Slack, Zoom

• 4+ years of experience in using Java under professional environment, or if you are non-Java user, excellent skills in generalized programming languages, such as Scala, Python, and Go.
• Interest and ability to learn other coding languages as needed.
• Experience with No
  
  SQL databases and 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.
• Business level of English or Japanese.
• Hands‑on experience with AI/LLM tools (e.g., ChatGPT, Git Hub Copilot, Gemini, Code Whisperer, or similar) in professional software development.

• Experience with implementing platform components such as RESTful APIs, Pub/Sub Systems, Database clients.
• Experience with AWS services.
• Experience in working for system development in finance, payment, or similar industries.
• Experience in system design, development of web systems which handle massive amount of transactions or require scalability.
• Language ability in Japanese and English is a plus (we have a professional translator but it is nice to have language skills).
• Experience in microservices.
• 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.

• Please refer Pay Pay 5 senses to learn what we value at work.

• Pay Pay Card:
  Backend Engineer

What is differences with Pay Pay (Please choose the position that best aligns with your career goals, as we do not allow simultaneous applications for two positions）

• Full Time

• Hybrid Workstyle (flexible working style…