Senior Software Engineer - Backend (FTC) at Boku

Boku Inc. (BOKU.L) is the leading global provider of local mobile-first payments solutions. Global brands including Amazon, DAZN, Meta, Google, Microsoft, Netflix, Sony, Spotify, and Tencent rely on Boku to reach millions of new paying consumers who do not use credit cards with our purpose-built payment network of more than 300 local payment methods across 70+ countries. Every year, Boku processes over $10 billion in value for our customers. Incorporated in 2008, Boku is headquartered in London and San Francisco and has employees in over 39 countries around the world, including Brazil, China, Estonia, Germany, Ireland, Japan, Singapore, and the UAE. Boku is a truly global company that takes pride in its diversity and thriving equal opportunity workplace. Role Purpose As a Senior Backend Software Engineer (Fixed Term Contract) within Boku’s Engineering organisation, you will be one of a small group of engineers delivering new products as part of Boku’s Innovation department. A new suite of products being built from the ground up. This is a greenfield development engagement: the work is scoped to designing and building new software, not maintaining or extending existing production services. You will work in a small, high-autonomy team with a clear remit and a defined delivery horizon, reporting to the Head of Product and Engineering. Key Responsibilities Backend Engineering • Design and build production-grade services using Java and Spring Boot, targeting high throughput, low latency, and high availability (99.99%+). • Implement and evolve RESTful/gRPC/MCP and event-driven APIs supporting payment initiation, callback handling, reconciliation, and settlement flows. • Build for fault tolerance and resilience: circuit breakers, retry logic, idempotency, and graceful degradation under load. Maximum observability and telemetry at the core of the build to ensure easy support. • Optimise service performance through profiling, load testing, and careful data access layer design (SQL and NoSQL). • Collaborating with colleagues and off-shore development teams providing code-reviews and guidance as necessary to team members and development studios. Payment Systems • Build the core components of Payout, Card Processing and FX systems from scratch, including a payout processing engine, AI agent treasury orchestration layer, and cash forecasting service. This work is entirely new development and there is no existing codebase to maintain or inherit. • Contribute to PCI DSS compliant system design and implementation, including sensitive data handling, audit logging, and access control. Frontend Contribution • Contribute React-based frontend components for internal tooling, operational dashboards, and merchant-facing interfaces where required. • Work with Product and Design to deliver functional, well-tested UI features that meet Boku's quality bar. FX & Treasury Integration (Desirable) • Support integration with FX data sources including Bloomberg feeds, for use in real-time rate pricing, settlement FX, and treasury risk tooling. • Contribute to cash position and FX exposure monitoring services, working alongside Finance and Treasury stakeholders. Reliability & Operations • Instrument projects with observability from day one: structured logging, distributed tracing, metrics, and alerting built as part of the product, not retrofitted. On-call and incident management for existing Boku production services are outside the scope of this contract. • Instrument services with structured logging, distributed tracing, and metrics; contribute to SLO/SLA definitions and alerting. • Set up CI/CD pipelines, container build configuration (Docker/EKS), and code quality gating (SonarCloud, SAST) as new infrastructure built to Boku’s engineering standards and handed over as part of the finished product. Key Skills, Experience and Competencies Required • 5+ years of backend engineering experience, with deep expertise in Java and the Spring Boot ecosystem (Spring MVC, Spring Data, Spring Security). • Demonstrable experience building and operating high-throughput, high-availability distributed payment or financial services systems. • Strong understanding of payment system architecture: idempotency, exactly-once delivery, reconciliation, and settlement flows. • Experience with relational databases (PostgreSQL, MySQL) and messaging systems (Kafka, RabbitMQ, or equivalent). • Familiarity with container-based deployment (Docker, Kubernetes/EKS) and CI/CD pipeline tooling (GitHub Actions or equivalent). • Experience with PCI DSS compliant system design and secure coding practices. • Strong communication skills; ability to work effectively with Product, Architecture, and Operations in a globally distributed team. Preferred • React frontend development experience sufficient to contribute to internal tooling and dashboards. • Experience integrating with Bloomberg data feeds (BFIX, B-PIPE, or similar) or other real-time FX data sources. • Background in FX processing, treasury systems, or multi-currency settlement. • Experience with financial messaging standards (ISO 20022, SWIFT MT/camt formats). • Prior work in a payments processor, PSP, or fintech operating across multiple markets. AI & Agentic Systems • Practical experience building or integrating LLM-powered features into production services, including prompt engineering, tool/function calling, and structured output handling via APIs such as Anthropic or OpenAI. Familiarity with AWS Bedrock is ideal. • Experience designing or contributing to agentic workflows: multi-step autonomous processes where models plan, call tools, and act on results — including handling retries, failure modes, and human-in-the-loop checkpoints. • Familiarity with MCP (Model Context Protocol) or similar tool-use frameworks for connecting AI models to internal APIs, databases, and external services. • Comfortable using AI-assisted development tooling (e.g. Claude Code, GitHub Copilot, Cursor) as part of day-to-day engineering workflow, and able to reason critically about where AI assistance adds value versus where it requires human judgement. Qualifications • Bachelor's degree in Computer Science, Engineering, or equivalent practical experience. • 5+ years of professional software engineering experience in backend-heavy roles. • Prior experience in a regulated financial services or payment processing environment strongly preferred. Why Join Boku? Impact: Work on payment infrastructure that processes billions of dollars annually, serving some of the world's largest digital commerce platforms across 65 countries. Focus: A fixed term engagement with a clearly scoped remit, embedded within a high-calibre engineering team operating on greenfield and core platform work. Culture: A collaborative, inclusive engineering culture that values craft, rigorous thinking, and delivery. Boku is a genuinely global company with deep expertise in local payment markets. Benefits: Competitive day rate, flexible working arrangements, and Singapore-based team with global stakeholder exposure.