Backend Engineer

Remote OK - Anywhere in Japan
Full-time
October 20, 2025

Job Description

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

Qualifications

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.

Preferred Qualifications

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

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About PayPay

PayPay, a FinTech company that has achieved more than 69M users (as of May 2025) within around six years 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.

PayPay's 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.

Japanese Language Policy
At PayPay, there is a mixture of Japanese and English spoken. Around 80% of their product team’s discussions happen in English, and they have technical interpreters and translators on staff to facilitate any translation necessary. Some members can speak both English and Japanese, but some can only speak either English or Japanese.

PayPay doesn’t have an official shared language, but in practice English tends to be the primary language used for internal communications and technical discussions like code reviews.

Instead of requiring that everyone be able to speak a specific language, PayPay expects an ability to communicate with mutual respect and a drive to ensure that you’re understood. The product team values proactive communication highly.
Visa Sponsorship
PayPay sponsors visas for applicants from overseas.
Paid Leave
- Days Off: Saturdays and Sundays. National holidays. Year-end and New Year holidays.
- Holidays: Annual paid leave, congratulatory or condolence leave, maternity leave and etc.
Benefits
🌎 Translation/interpretation support (EN<>JP)

🧡 Support for translation or other administrative tasks in Japanese

👍 Support from bilingual PIC for engineers

🇯🇵 Free Japanese lessons on company time

💻 PC and phone are given (based on the company’s regulations)

👩‍🎓 Training Program: We have various training programs for different kinds of needs

💜 Social security/insurance benefits included

💛 Defined contribution pension system (TBC)

🏥 Health insurance

🚃 Transportation coverage (up to ¥150,000/mo)
Engineer Interview Process
PayPay's Hiring process are as below:
- Application Review (English CV is required)
- Coding Test or Take Home Assignment (only applied to required positions)
- 3-4 Interviews (including both technical and behavioral interviews)
- Offer Meeting
Remote Work
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.
Work style
- Super Flex Time with no core time
- In principle, from 9:00am-5:45pm (actual working hours: 7h45m + 1h break)