Kotlin Backend Engineer (FreelanceService Agreement)

We are looking for a skilled Kotlin Backend Engineer for service agreement collaboration. B2B Sales & Distribution team builds and operates the backend platform powering Flixs partner-facing ecosystem including a self-management platform for partners a back office portal for internal users and an AI agentic bot supporting partner operations. The team is driving a significant modernization of its backend architecture and is working in an AI-native development environment.

Scope of services

• Independent delivery of backend services in Kotlin and Spring Boot including design development and maintenance
• Building and maintaining REST APIs used by internal and external partners
• Contributing to architectural decisions and technical modernization initiatives as a senior topic driver
• Improving observability performance and reliability of backend systems using DataDog
• Supporting CI/CD pipelines and cloud infrastructure on AWS and Kubernetes
• Working within an AI-native development environment including CI-integrated code review automation and an internal Claude Code plugin marketplace covering Kotlin/Spring Boot conventions architectural patterns testing practices and database guidelines
• Sharing Kotlin expertise and best practices with existing engineers on the Flix team who are transitioning from other languages through code review pairing and technical guidance

Relevant expertise

• 4 years of software engineering experience primarily backend development with a JVM language including some commercial experience with Kotlin
• Hands-on Spring Boot experience
• Experience building and maintaining REST APIs and distributed systems
• Solid SQL knowledge and relational database design including MySQL and PostgreSQL
• Sound software engineering fundamentals and clean code practices
• Clear written and spoken English communication skills
• Preferred experience with: AWS Kubernetes GitLab CI/CD Kafka Terraform LLM integrations RAG systems AI product development or legacy system migration experience

Collaboration model

• Cooperation based on a service agreement with independent delivery of agreed services and invoicing