Backend Engineer

About PayPay

PayPay, a FinTech company that has achieved more than 70M (as of July 2025) since its launch in 2018, is rapidly expanding its business scale as a payment platform used by approximately one out of every two smartphone users in Japan.

The company has a diverse team of professionals from more than 50 countries and is building a world-class engineering organization.

Our biggest competitor is "cash". They are seeking people who can accept this challenge positively, brush up on the product at a tremendous speed that other companies could never achieve, and who are passionate about promoting and spreading such a financial life platform in a short time along with professionalism.

PayPay is committed to maintaining a "Day 1" mindset, bringing to life visions of the future that no one else can even imagine. At PayPay, we provide an environment where everyone can deliver outstanding performance as professionals, through a flexible work style that includes remote and office.

Experience life in Japan
Featured life in Japan

Position

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

AI-First Culture at PayPay

At PayPay, 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.

Main Responsibilities

• 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.

Tech Stack

We select the best combination of tech at times.
| Java, Kotlin, Scala
| Spring Boot, JUnit, Reselience4j, Feign
| MySQL/AuoraDB, DynamoDB, ELK, Kafka, Redis, TiDB
| Docker, Kubernetes, ArgoCD, AWS, GCP
| GitHub, IntelliJ, Gradle, Maven, npm/yarn, Flyway, Jenkins, snyk,
| Bigquery, Kibana, Spark
| PlantUML, draw.io, miro.com
| Slack, Zoom

Your qualification

• 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 NoSQL 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, GitHub Copilot, Gemini, CodeWhisperer, or similar) in professional software development.

Will be a plus

• 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.

What we offer

• Social Insurance (health insurance, employee pension, employment insurance and compensation insurance)
• 401K
• Translation/Interpretation support
• VISA sponsor + Relocation support

Additional details

PayPay 5 senses

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

Working Conditions 

Employment Status

• Full Time

Office Location

• Hybrid Workstyle (flexible working style including Remote and office)
  *There are no fixed rules regarding office attendance in Product group; it depends on each individual's discretion.

• LIFE in JAPAN FACTBOOK

Work Hours

• Super Flex Time (No Core Time)
• In principle, 9:00am-5:45pm (actual working hours: 7h45m + 1h break)

Holidays

• Every Sat/Sun/National holidays (In Japan)/New Year's break/Company-designated Special days

Paid leave

• Annual leave (up to 14 days in the first year, granted proportionally according to the month of employment. Can be used from the date of hire)
• Personal leave (5 days each year, granted proportionally according to the month of employment)
  *PayPay's own special paid leave system, which can be used to attend to illnesses, injuries, hospital visits, etc., of the employee, family members, pets, etc.

Salary

• Annual salary paid in 12 installments (monthly)
• Based on skills, experience, and abilities
• Reviewed once a year
• Special Incentive once a year *Based on company performance and individual contribution and evaluation
• Late overtime allowance
  
  *Payroll payment can be changed to digital salary payment “PayPay Paycheck” for an amount set by you