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Our client is a Greek technology company specializing in secure communications and command-and-control systems for defense, security, and public safety. It develops advanced software solutions for incident management and crisis response, supporting mission-critical operations. The company operates internationally and focuses on high-security, intelligence-driven technologies for complex environments.

Key Responsibilities

• Feature Development: Develop and maintain high-quality Java 21/Spring Boot backend services, managers, controllers, and processing pipelines for a mission-critical C4I command server.
• Real-Time Communication: Implement and support low-latency Netty WebSocket flows for control, session, voice, and fanout traffic using protobuf-based message contracts.
• Performance Engineering: Contribute to low-latency, high-throughput systems by improving p50/p99 latency, reducing allocation pressure, applying backpressure-aware design, and validating changes with JMH benchmarks.
• Lock-Free Concurrency: Implement thread-safe features using concurrent and lock-free data structures where appropriate, reason about CAS contention, avoid unnecessary blocking, and preserve correctness under high load.
• MongoDB Data Implementation: Implement and optimize MongoDB persistence, query patterns, indexes, aggregation-style reads, and live repository cache synchronization for tenant, agent, geofence, media, health, and workflow data.
• Redis, Caching & Pub/Sub: Implement Redis/Jedis-backed caching, Spring Session support, pub/sub event propagation, retry handling, connection-pool tuning, and single-node or clustered Redis integration.
• API & Protocol Contracts: Build secure REST endpoints and OpenAPI-documented contracts, validate request/response models, and keep REST and protobuf interfaces stable for mobile, desktop, and command-center clients.
• External Integration Implementation: Implement reliable integrations with spatial/map providers, Traccar/WebSocket feeds, weather/GeoJSON services, and third-party APIs, including transformation, retries, and error handling.
• Security Implementation: Apply Spring Security controls, JWT validation, TLS/SSL configuration, IP/request filtering, input validation, safe secret handling, and license-aware runtime behavior as directed by senior engineers.
• Quality Assurance & Reliability: Write maintainable unit, integration, concurrency, and regression tests using JUnit, Spring Boot test support, and Testcontainers for MongoDB/Redis-backed workflows.
• Collaboration: Work closely with backend leads, frontend, mobile, and desktop teams to refine API contracts, troubleshoot real-time data flow, and review production-minded implementation details.

Required Qualifications

• Experience: 3-5 years of professional backend development experience, with strong hands-on experience building Java/Spring Boot services.
• Core Java Proficiency: Strong knowledge of Java, object-oriented design, collections, concurrency, asynchronous execution, and practical Java 21 development patterns.
• Spring Boot Backend Skills: Practical experience with Spring Boot web applications, validation, security, configuration, actuator/health endpoints, and production-ready service design.
• Real-Time Systems: Working knowledge of WebSockets, Netty, protobuf or similar binary protocols, fanout, streaming-style processing, and low-latency delivery patterns.
• Data & Middleware: Proven experience with MongoDB and Redis/Jedis for persistence, caching, pub/sub, session data, indexes, query tuning, and connection-pool behavior.
• API & Security: Solid understanding of RESTful API design, OpenAPI/Swagger documentation, JWT, SSL/TLS, input validation, and secure backend implementation practices.
• Performance Mindset: Ability to reason about throughput, tail latency, lock-free algorithms, CAS contention, thread safety, memory allocation, and benchmark or profile changes before and after implementation.
• Testing: Expertise writing robust unit and integration tests for Spring Boot applications, preferably with Testcontainers-backed MongoDB and Redis scenarios.
• Soft Skills: Excellent problem-solving skills, attention to detail, ownership of assigned features, and ability to contribute constructively to code reviews.

Nice-to-Have Skills

• Experience with real-time communication systems and WebSocket-based applications.
• Familiarity with performance optimization and high-throughput backend systems.
• Experience working with NoSQL databases and caching technologies.
• Knowledge of secure software development and backend security best practices.
• Exposure to third-party system integrations and API-driven architectures.

What They Offer

They are committed to investing in the well-being, professional growth, and overall satisfaction of their team members. As part of their benefits package, they offer:

• Hybrid Working: Exploring a hybrid work approach could provide flexibility and improved work-life balance, with the understanding that arrangements will be evaluated and adjusted as needed to align with organizational priorities and team needs.
• Performance Bonus: Receive a performance-based bonus calculated as a percentage of your annual salary, rewarding your contributions and success.
• Private Health Insurance: Comprehensive private health insurance coverage to safeguard your health and peace of mind.
• Learning & Development Budget: Access a dedicated budget for online courses,certifications, and professional development programs to support your continuous learning journey.
• Vouchers & Discounts: Enjoy vouchers for essential goods, services, and recreational activities to enhance your lifestyle.
• Multifaceted Knowledge & Internal Training: Take part in internal training programs designed to provide a holistic understanding of their business and industry. They emphasize cross-functional learning to empower you with diverse skills and knowledge.