Senior Backend Engineer – Kotlin, Spring Boot

E.ON

full-time

Posted on:

Location Type: Hybrid

Location: Köln • Germany

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Job Level

Senior

Tech Stack

AWSCloudGraphQLKotlinSpringSpring BootSpringBoot

About the role

  • Develop small, focused backend services in Kotlin and Spring Boot using cloud-native technologies for integrations and custom business logic
  • Design and implement event-driven architectures on AWS
  • Design, specify and implement APIs (REST and GraphQL), including versioning, documentation (e.g., OpenAPI), and authentication/authorization concepts (e.g., OAuth2, JWT)
  • Review and enforce provider-side API contracts to ensure backward compatibility and secure API evolution
  • Integrate third-party services such as payments, credit checks, notifications, or document workflows
  • Take end-to-end responsibility for backend delivery: development, deployment and production readiness
  • Implement and maintain Infrastructure as Code and CI/CD pipelines for your services in GitLab
  • Ensure security, reliability and observability are considered throughout the design
  • Work closely with Architecture, Operations and QA in Agile/Scrum teams
  • Use AI agents for autonomous code generation and focus on strategic reviewing, architecture and efficient human-in-the-loop processes

Requirements

  • Several years of experience as a Backend Engineer, ideally with cloud-native architectures on AWS
  • Strong knowledge of Kotlin / Spring Boot and experience building API-driven integrations
  • AI-native developer mindset: proficient with agent-driven workflows using tools like Claude Code, Cursor (Composer) or Windsurf (Cascade)
  • Practical experience with DevOps fundamentals: CI/CD, Infrastructure as Code, cloud deployments
  • Solid understanding of API-first systems (REST/GraphQL) and asynchronous integrations
  • Strong ownership mentality and ability to collaborate across teams
  • Confident communication in German and English
Benefits
  • A highly motivated team with flat hierarchies and short communication paths
  • An office in the heart of Cologne and the option for hybrid work
  • Lots of fun at work and within the team
  • Competitive pay and 30 days of vacation per year
  • Subsidized job ticket and free parking spaces
Applicant Tracking System Keywords

Tip: use these terms in your resume and cover letter to boost ATS matches.

Hard Skills & Tools
KotlinSpring BootAWSRESTGraphQLOpenAPIOAuth2JWTInfrastructure as CodeCI/CD
Soft Skills
ownership mentalitycollaborationcommunication