Senior Backend Software Developer - Java/Spring Boot (m/f/d)

Our brand Deutsche Telekom IT Solutions Slovakia entered the life of Košice region in 2006 under the name of T-Systems Slovakia and ever since has been inextricably linked with the region when became one of the founding members of Košice IT Valley. We have managed to grow from scratch to the second largest employer in the eastern part of the country with more than 3900 employees. Our goal is to proactively find new ways to improve and continuously transform into the type of company providing innovative information and communication technology services.

We are looking for a Senior Backend Developer/Engineer to join the team behind Charisma and take a leading role in building, scaling, and stabilizing a solution that supports complex operational and rollout processes.

You will work on backend services at the core of the solution, leading complex technical topics around microservices, integrations, data, performance, security, and system reliability. This is a senior hands-on engineering role where you will shape technical decisions, improve existing production services, and guide how new functionality is designed, delivered, and operated.

You will be part of an agile delivery environment where backend, frontend, quality, and business experts work together to turn real business requirements into reliable software. As a senior team member, you will also collaborate closely with customers, stakeholders, architects, and delivery leads to clarify needs, propose solutions, manage technical expectations, and ensure the solution brings measurable business value.

WHAT WILL YOU DO?

• Lead the design, development, and continuous improvement of backend services using Java 17+ and Spring Boot
• Define and evolve microservices and REST APIs used by the Charisma solution, ensuring scalability, maintainability, security, and operational reliability
• Translate complex business and customer requirements into robust, maintainable, and scalable technical solutions
• Drive performance optimization, technical stabilization, and root-cause analysis of production services
• Design data models and lead work with PostgreSQL, SQL optimization, database migrations, and data consistency topics
• Apply and promote engineering approaches such as Domain-Driven Design, Event-Driven Architecture, Clean Architecture, and established design patterns
• Design, review, and document APIs using OpenAPI / Swagger, ensuring they meet integration and stakeholder needs
• Lead and support integrations using REST and TARDIS, including troubleshooting and technical alignment with consuming systems
• Define and improve automated unit, integration, API, performance, and load testing strategies
• Work with Docker, Kubernetes, Git, and CI/CD to improve development, deployment, and operational practices
• Improve application observability and troubleshooting using Prometheus, Grafana, LUMINA, OpenTelemetry, and logging
• Collaborate with frontend engineers, quality engineers, business experts, customers, and stakeholders to deliver end-to-end functionality
• Provide technical guidance, code reviews, mentoring, and support to other engineers working on the same project
• Contribute to rollout activities, technical planning, risk identification, and continuous improvement of the overall solution

YOU WILL SUCCEED IF YOU:

have:

• Extensive hands-on experience with Java 17+, Spring Boot, and the Spring Framework, including production-grade enterprise applications
• Strong experience designing, developing, and operating microservices and REST APIs in complex system landscapes
• Advanced knowledge of PostgreSQL, SQL, data modeling, performance tuning, and database migration strategies
• Deep experience with Spring Data JPA, Hibernate, Spring Security, Spring Web, and Spring Validation
• Strong understanding of modern software architecture and engineering principles, including DDD, Event-Driven Architecture, Clean Architecture, design patterns, and API design best practices
• Experience making technical design decisions and explaining trade-offs to engineers, architects, customers, and non-technical stakeholders
• Experience with Maven or Gradle and strong understanding of build, dependency, and release management
• Strong experience with automated testing using technologies such as JUnit 5, Mockito, Testcontainers, and API testing tools
• Proven experience with performance and load testing of large-scale applications, including analysis and remediation of bottlenecks
• Practical production experience with Git, Docker, Kubernetes, and CI/CD
• Strong understanding of observability, monitoring, logging, alerting, and production troubleshooting
• Experience working with REST-based integrations and TARDIS
• Excellent communication skills and proven ability to work directly with customers, stakeholders, architects, delivery leads, and cross-functional teams
• Ability to mentor developers, perform high-quality code reviews, and promote engineering standards within the team
• And you speak English (min. B2 level).

Nice to Have:

• Experience with AWS and cloud-native application design
• Knowledge of Kotlin
• Experience with Reactive Programming / WebFlux
• Knowledge of route optimization technologies
• Experience leading technical workshops, solution reviews, or customer-facing technical discussions
• Experience with architectural documentation, technical roadmaps, and production readiness reviews

WHY SHOULD YOU CHOOSE US?

We believe in balance between work and personal life. An attractive and extensive work-life balance portfolio guarantees lasting motivation for employees and thus a better quality of life, promotes physical and mental well-being and contributes to a positive work environment. All this with the aim of providing more freedom in reconciling work, career growth, private life and individual lifestyle. Therefore we offer to our employees over 25 different benefits to improve their personal and professional life in these areas:

• Financial benefits
• Benefits with focus on learning and development
• Benefits with focus on health and sport
• Benefits with focus on family and work - life balance
• Other benefits

For more information about our benefits click to Benefits

Salary

Final salary is negotiable.

We are offering base salary depending on seniority level and previous experience of candidate. In addition to base salary we provide variable part and other financial benefits. Base salary will not be lower than 3100€ /brutto.

Additional information

* Please be informed that our remote working possibility is only available within Slovakia due to European taxation regulation.