Senior Java / Spring Boot Engineer

We are seeking a Senior Java / Spring Boot Engineer to design and build high-throughput, real-time backend services for a mission-critical $24/7$ security control platform used by a major European public transport network. In this role, you will help build a resilient web application from scratch to replace a decades-old legacy system, handling real-time events, vehicle locations, video streams, radio, and multi-organization collaboration under strict high-availability and sub-second latency requirements.

Key Responsibilities

• Real-Time & Event-Driven Services: Build robust event processing services using Java 17+ and Spring Boot that handle sudden alarm peaks and high-throughput data streams gracefully.

• System Integrations & Connectors: Design resilient connectors to field equipment and partner systems (alarms, radio, telephony, video, vehicle positioning) with advanced retry mechanisms, monitoring, and error handling.

• Access Control & Multi-Tenancy: Implement secure multi-organization access control, role-based permissions, and data isolation across collaborating enterprise entities.

• Collaboration & Co-Editing Features: Develop backend mechanisms for real-time incident co-editing, allowing operators from different organizations to work on incidents simultaneously.

• AI-Assisted Engineering: Drive AI coding agents (Claude Code, Cursor, Copilot) to implement isolated modules, carefully reviewing output and maintaining strict accountability for code quality, security, and performance.

• Quality & Automated Testing: Write comprehensive unit, integration, and contract tests alongside specifications, ensuring nightly automated runs remain green.

Product & Technical Environment

• Core Tech Stack: Java 17+, Spring Boot, PostgreSQL, Event-Driven Architecture (message brokers/queues), REST APIs, Docker, CI/CD.

• Frontend & Real-Time Integrations: Close collaboration with React/TypeScript developers on API contracts, GIS mapping, browser video streaming, and WebSockets/SSE.

• Delivery Framework: AI-first, spec-driven methodology with explicit interface contracts, short sprints, and regular production releases.

Required Profile & Qualifications

• Commercial Experience: 7+ years of professional backend engineering experience with strong, hands-on expertise in Java (17+) and Spring Boot.

• Complex Enterprise Systems: Proven experience building complex custom applications featuring high-throughput workflows, multi-tenant permissions, or time-sensitive integrations.

• Event-Driven Architecture: Strong expertise in asynchronous/event-driven systems, message brokers, and low-latency, high-availability stream processing.

• Data Modeling & Databases: Advanced knowledge of PostgreSQL schema design, transactional management, query optimization, and concurrency handling.

• Testing Culture: Deep familiarity with TDD/BDD practices, contract testing, unit/integration test suites, and CI/CD automation pipelines.

• Languages: Professional fluency in English (B2/C1). Knowledge of French is a strong advantage.

Nice to Have

• Experience with message brokers such as Kafka or RabbitMQ.

• Hands-on exposure to WebSockets, Server-Sent Events (SSE), GIS/PostGIS geospatial data, or browser-based video streaming.

• Background in public transport, public sector, security control centers, or mission-critical real-time platforms.

What We Offer

• Opportunity to build core European public infrastructure using a clean codebase, modern AI tooling, and zero tech debt.

• 100% remote flexibility with strong engineering practices (pair programming, code reviews, spec-driven delivery).

• Long-term engagement and competitive compensation under a B2B contract