Senior Java Backend Engineer

Qualco Group; Kentucky; Hybrid; USD 110,000 - 180,000; Full time

Benefits offered by this job

Ticket restaurant card

Annual bonus programs

Modern IT equipment

Health insurance

Job summary

Quento Technologies S.A., the ICT arm of the Qualco Group, seeks a Senior Java Backend Engineer to design, build, and maintain scalable backend services. You will work on microservice architectures, event-driven systems, and cloud-native apps using Java 21 and Spring Boot, collaborating with DevOps and platform teams.

Your responsibilities include designing RESTful APIs, implementing gRPC, Kafka-based event processing, and integrating with OIC, Salesforce, and SAP ISU.

Qualifications

• Bachelor's degree in computer science, engineering, or related field.
• 3–5+ years backend development experience.
• Strong hands-on with Java (preferably Java 21) and modern language features.
• Proven experience with Spring Boot microservices, REST controllers, data access, and security.
• Experience migrating apps 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.
• Strong backend security knowledge (OAuth2, OIDC, RBAC).
• Experience writing automated unit/integration tests.
• Experience in Agile environment.

Responsibilities

• Design and develop backend microservices using Java 21 and Spring Boot 3.x.
• Build and maintain RESTful APIs with OpenAPI/Swagger specifications.
• Implement gRPC services/clients and Protobuf design.
• Develop event-driven solutions with Apache Kafka.
• Integrate with external systems (OIC, Salesforce, SAP ISU).
• Implement OAuth 2.0/OIDC authentication/authorization.
• Write unit and integration tests with JUnit 5, Mockito, Testcontainers.
• Collaborate with DevOps on Docker/Kubernetes deployments.
• Ensure compliance with group policies and regulatory requirements.

Skills

Java 21

Spring Boot

Microservices

REST APIs

OAuth 2.0 / OIDC

Kafka

Testing

DevOps familiarity

Education

University degree in CS/Engineering

Tools

OpenAPI/Swagger

gRPC

Protobuf

PostgreSQL

Redis

Docker

Kubernetes

Job description

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.

• 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.

Your Life @ QualcoGroup

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 the Recruitment Notice, before the submission of your application.