Senior Java Backend Engineer

At Quento Technologies S.A., the ICT arm of the Qualco Group, we deliver comprehensive and innovative solutions across AI, Digital Engineering, Cloud, and Cybersecurity, helping businesses accelerate digital transformation. With a presence in Greece, Luxembourg, and Belgium, and backed by the expertise of the Qualco Group, we combine deep technical knowledge with strategic partnerships to support business growth.

At Quento Technologies S.A. we empower our people to innovate and lead in delivering transformative ICT solutions to our clients worldwide. Quento Technologies S.A. seeks a highly motivated and experienced Senior Java Backend Engineer to design, build, and maintain modern, scalable backend services. You will work on microservice-based architectures, event-driven systems, and cloud-native applications using modern Java and Spring Boot, collaborating closely with DevOps and platform teams.

Your responsibilities will entail:

• Design and develop backend microservices using Java 21 and ** Spring Boot 3.x;**
• Build and maintain RESTful APIs with clear error handling and documented ** OpenAPI/Swagger** specifications;
• Implement **gRPC services and clients **, including Protobuf schema design;
• Develop event-driven solutions using ** Apache Kafka** consumers and producers;
• Integrate backend services with external systems (OIC, Salesforce, SAP ISU);
• Implement authentication and authorization using **OAuth 2.0 / OIDC **, including token validation and role-based access;
• Write unit and integration tests using JUnit 5, Mockito, and Testcontainers;
• Collaborate with DevOps teams on containerized deployments in Docker and Kubernetes;
• Ensuring that all activities and duties are carried out in full compliance with regulatory requirements and supporting the continued implementation of the Group Anti-Bribery and Corruption Policy.

Requirements

• University degree in Computer Science, Engineering, or a related field;
• 3–5+ years of experience in backend development;
• Strong hands-on experience with Java (preferably Java 21) and modern language features;
• Proven experience with Spring Boot (microservices, REST controllers, data access layers, security);
• Experience migrating applications from older Java versions (e.g., Java 11);
• Solid knowledge of Kafka-based event-driven architectures;
• Experience with **PostgreSQL **, ** Azure Cosmos DB , and ** Redis;
• Good understanding of containerization (Docker) and Kubernetes fundamentals;
• Strong understanding of backend security concepts (OAuth2, OIDC, RBAC);
• Experience writing automated tests at unit and integration level;
• Experience working in an Agile environment;

Nice to Have

• Integration experience with Confluent Kafka or ** Azure Event Hubs;**
• Exposure to AKS environments;
• Previous work with enterprise integrations (Salesforce, SAP ISU);
• Familiarity with cloud-native observability tools;
• Familiarity with Azure DevOps.

Benefits

Your Life @ Qualco Group

On top of challenging work environment, we are offering:

💸 Competitive compensation, ticket restaurant card, and annual bonus programs

💻 Cutting-edge IT equipment, mobile and data plan

🏢 Modern facilities, free coffee and beverages, indoor parking, and company bus

👨‍⚕ Private health insurance, onsite occupational doctor, and workplace counselor

🏝️ Flexible working model, hybrid benefits & home equipment benefits

🤸‍♂️ Onsite gym, wellness facilities, and ping pong room

💡 Career and talent development tools

🎓 Mentoring, coaching, personalized annual learning and development plan

🌱 Employee referral bonus, regular wellbeing, ESG and volunteering activities

Your race, gender identity and expression, age ethnicity or disability make no difference in Quento Technologies S.A. We want to attract, develop, promote, and retain the best people based only on their ability and behavior.

Disclaimer: Quento Technologies S.A. collects and processes personal data in accordance with the EU General Data Protection Regulation (GDPR). We are bound to use the information provided within your job application for recruitment purposes only and not to share these with any third parties. For more details on the processing of your personal data during the Recruitment procedure, please be informed in theRecruitment Notice, before the submission of your application.