Senior Software Engineer (Java)

Job brief

Our client, a well-funded, early-stage startup revolutionizing B2B payments, is looking for a Software Development Engineer to join their Platform team as a key technical contributor. The successful candidate will design, build, and maintain the core systems — including Spring Boot microservices, a Spring Boot BFF, and Kubernetes-based cloud infrastructure — that power secure, scalable payment processing for enterprise customers worldwide. They will own backend services and APIs, drive integrations with banking partners, and mentor other engineers while helping shape the platform architecture.

Responsibilities

• Own and evolve the platform's core architecture, including service boundaries, data models, and the shared libraries and infrastructure other teams build on.
• Design and implement secure, well-documented backend services and REST APIs, shaping API contracts and OpenAPI specifications.
• Design database schemas, caching strategies, and event-driven, message-based workflows that keep high-volume transaction processing consistent, performant, and resilient.
• Champion system reliability and security across the platform, including monitoring, alerting, error handling, data encryption, and secure API design that meets the standards of a regulated financial environment.
• Build and maintain secure, scalable integrations with major financial institutions and payment networks, translating complex banking protocols into robust, reusable platform capabilities.
• Implement high-volume transaction processing systems with the accuracy, idempotency, and auditability that financial operations require.
• Partner with Product, Architecture, and Engineering teams to translate business requirements into platform solutions, drive technical decisions, and advocate for reliability and security in architectural discussions.
• Mentor mid-level and junior engineers on backend best practices, code quality, system design, and platform engineering principles.
• Lead code reviews, establish coding standards, and help shape engineering culture as the team grows.

Requirements

• 7+ years of software engineering experience with a strong focus on backend and distributed systems.
• Expert proficiency in Java and the Spring framework (Spring Boot), with a track record of building complex, high-scale backend systems.
• Deep experience designing and building microservices and REST APIs, including OpenAPI-driven contracts and generated clients.
• Hands-on experience with containerization and orchestration (Docker, Kubernetes) and cloud platforms (AWS, GCP, or Azure).
• Strong system design skills across distributed systems, including database design, caching strategies, and message queues or event-driven architectures.
• Solid understanding of authentication and security best practices (OAuth2/OIDC, data encryption, secure API design) in a financial services context.
• Proven ability to debug complex issues, optimize performance, and architect solutions for high-scale, high-availability systems.
• Strong proficiency with modern AI coding assistants (e.g., Claude Code, GitHub Copilot, or similar), with a track record of using them to boost engineering speed, quality, and impact.
• Excellent communication skills and experience collaborating in cross-functional agile teams.
• Professional fluency in English (written and verbal); all engineering collaboration, documentation, code reviews, and stakeholder communication are conducted in English.

Nice to have

• Experience with real-time payment systems or high-frequency transaction processing.
• Knowledge of banking APIs, SWIFT messaging, or ACH processing.
• Experience with event-driven architectures and stream processing.
• Background in fintech, payment processing, or B2B financial platforms.
• Familiarity with enterprise DevOps practices and infrastructure as code.
• Experience building multi-tenant SaaS applications with organization-scoped data access.
• A track record of leading backend architecture decisions and establishing engineering standards.

What's on offer

• Foundational technology ownership — they'll own core platform services that process millions in B2B payments, directly powering how enterprise customers manage counterparties, execute payments, and maintain compliance.
• A real technical voice — their opinions on service architecture, API contracts, and data design will directly shape how the stack is built; this is a role that defines systems, not just maintains them.
• A modern stack — a thoughtfully chosen technology stack that values simplicity and pragmatism over hype, with new tools adopted where they add real value.
• Early-stage impact — a well-funded startup where their contributions will shape both the product and the engineering culture from the ground up.
• An AI-forward culture — AI is embraced as a tool for innovation and efficiency, with curious, adaptable engineers welcome to bring it into their work.
• A strong, growing team — a diverse team, including engineers from SAP and fintech innovators, who value technical excellence, continuous learning, and work-life balance.