Guide a team of three engineers while architecting payment systems that power millions of transactions.

If you've been waiting for the right opportunity to lead with
Scala and functional programming principles
, this is it.

THE OPPORTUNITY FOR FUNCTIONAL PROGRAMMING ENGINEERS

• Work with a modern functional tech stack.
  Built on Scala with cats-effect, event sourcing patterns with Kafka, and constantly evolving toward better FP practices.
• Your team sits at the business core.
  Build payment APIs and backend systems that Japan's largest e-commerce merchants integrate directly—real transactions, real impact, real-time.
• FP mentorship is expected.
  Engineers have joined without FP backgrounds and grown through pair programming and team learning. You'll guide this growth while staying hands-on with code.
• Influence technical direction.
  Partner with the Head of Engineering to set architecture standards, modernize the stack, and establish best practices—not just execute someone else's vision.
• Lead without losing technical depth.
  Three direct reports means you architect solutions, review code, and write production systems while developing leadership skills.

YOUR CORE RESPONSIBILITIES

• Lead technical planning for merchant-facing payment systems, translating requirements into solutions your team executes with confidence.
• Build backend services meeting fintech security, compliance, and resilience standards through fail-safe designs and proactive incident prevention.
• Mentor engineers in FP concepts and technical skills via code reviews, architectural discussions, and hands-on collaboration.
• Design APIs considering architecture tradeoffs, communicating decisions to both technical teams and business stakeholders.
• Partner cross-functionally to align engineering solutions with product and business strategy.

REQUIRED BACKGROUND

• 5+ years backend engineering in agile environments with production systems
• Proficient in statically-typed languages (Scala, Java, Kotlin, Rust) with genuine FP interest
• Strong grasp of software architecture, system design tradeoffs, and service alignment
• Quality-focused approach: readable code, systematic debugging, automated testing as standard practice
• Comfortable with knowledge sharing, cross-team collaboration, and translating technical concepts for non-technical audiences
• Interest in connecting engineering strategy to product development and business goals
• Work Authorization:
  Must be Japan-based or hold valid Japanese work visa

NICE TO HAVE

• Experience with: Scala, Cassandra, Kafka, Postgres, REST APIs, microservices, event sourcing, cats-effect, distributed systems
• Understanding of event sourcing patterns in Kafka
• Technical leadership or mentorship background
• Payments platform or fintech experience

TECH STACK & ENVIRONMENT

Stack:
AWS, Scala (cats-effect), Akka, Kafka, Cassandra, Elasticsearch, Docker, Terraform, CircleCI, DataDog

Team:
International environment with colleagues from 35+ countries

Location:
Hybrid model—central Tokyo office twice weekly, complete flexibility otherwise, no core hours

Scale:
Enabling e-commerce transactions across Japan's biggest platforms

Culture:
Minimal overtime, strong work-life balance, growth-oriented scaling phase

APPLY CONFIDENTIALLY

Send your CV to

— all applications handled with complete confidentiality.