BFF Backend Engineer (Java / Kotlin) — Mobile Payments Platform — Tokyo

Location requirement

You must already be living in Japan with valid work authorization. We are not sponsoring relocation or visa transfers from overseas for this role. Applications from outside Japan will not be considered.

The context

Abbeal is hiring two BFF Backend Engineers on permanent contracts, for a long-term engagement with a leading Japanese mobile payments company. You join the product engineering organisation and work on the backend-for-frontend layer of a payment system used at national scale: large-scale distributed design, very high throughput, strict reliability requirements. Two openings, permanent position at Abbeal, target start 16 August 2026 (the start date can move if hiring takes longer).

What you will do

• Design and build BFF services for a high-traffic payment platform in Java, Kotlin and Spring Boot
• Work on large-scale, high-throughput distributed systems: concurrency, resilience patterns (Resilience4j, Feign), distributed caching
• Integrate relational and NoSQL stores (MySQL / Aurora, DynamoDB, TiDB) together with Kafka and Redis
• Ship through the existing delivery chain: Docker, Kubernetes, ArgoCD, Jenkins, Gradle/Maven, Flyway, Snyk on AWS and GCP
• Contribute to code reviews, testing (JUnit) and technical documentation alongside the product teams

What we are looking for (must-have)

• Currently based in Japan with valid work authorization — no relocation or visa sponsorship from overseas for this role
• 4+ years of professional Java experience, or an equally strong level in Scala, Python or Go
• Hands-on experience with NoSQL databases and distributed caching
• Solid fundamentals: data structures, algorithms, object-oriented design
• Comfortable with concurrency and distributed computing
• A CS or Computer Engineering degree, or 5+ years building SaaS platforms
• Business-level English or Japanese
• AI-first practice: daily, demonstrable use of AI and LLM tooling (Copilot, ChatGPT, Gemini, CodeWhisperer) for coding, review, testing, documentation and debugging. The client treats AI-assisted engineering as non-optional and will probe it during interviews.

Nice to have

• RESTful APIs, Pub/Sub systems, database clients
• AWS services
• Finance, payments or fintech background
• Web systems with very high transaction volume or strong scalability constraints
• Microservices architecture
• Japanese in addition to English (a professional interpreter is available in-house)
• A track record of embedding AI into design and delivery, or open source AI contributions

Practical details

• Location: Tokyo, hybrid. No fixed office attendance rule in the product group, left to individual discretion.
• Hours: Super Flex, no core time. Reference day 9:00 to 17:45 with a 1-hour break (7h45 effective).
• Contract: permanent position (full-time employee) at Abbeal, on a long-term project. Target start 16 August 2026.
• Openings: 2
• Working language: English or Japanese at business level.

Working with Abbeal

Abbeal is an engineering company operating across Paris, Montreal and Tokyo. You are hired by Abbeal on a permanent contract and work on a long-term project with our client: we carry the employment relationship, the client relationship and the administrative side, and we stay involved over the long run. Questions before applying? Write to recrutement (at) abbeal.com.