Senior Software Engineer - Backend

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 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 re...