mid-level backend engineer

We are seeking a highly proficient Mid-Level Backend Engineer to serve as a core contributor to our client’s mission-critical EPTTA C4I backend server. This role is responsible for the end-to-end development,testing, and implementation of high-volume, low-latency server features across Java 21, Spring Boot,REST APIs, Netty WebSocket transport, protobuf message flows, MongoDB persistence, and
Redis-backed caching, session, and pub/sub infrastructure.

The ideal candidate will possess a strong foundation in secure coding, concurrent programming, lock-free design principles, and performance engineering, working independently on complex features within the established architectural framework.

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.

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.

Benefits Package

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.