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Kotlin Backend Engineer - (Freelance/Service Agreement)

1 hour ago
Poland
Freelance
Mid Level
Backend Engineer
Software Development
AWS CI/CD Datadog Kafka Kotlin Kubernetes MySQL PostgreSQL REST API Spring Boot SQL Terraform
Apply Now

Flix SE

Flix provides long-distance bus and train travel solutions through its brands FlixBus, FlixTrain, Greyhound, and Kâmil Koç. It operates as an asset-light travel-tech platform that combines network planning, marketing, pricing, and technology to connect travelers with transport partners.

Travel tech
1001-5000
Founded 2011
View All Jobs 5

Description

  • Deliver backend services in Kotlin and Spring Boot, including design, development, and maintenance.
  • Build and maintain REST APIs for internal users and external partners.
  • Contribute to architectural decisions and technical modernization initiatives.
  • Improve observability, performance, and reliability of backend systems using DataDog.
  • Support CI/CD pipelines and cloud infrastructure on AWS and Kubernetes.
  • Work in an AI-native development environment with code review automation and internal tooling.
  • Share Kotlin expertise through code review, pairing, and technical guidance for engineers transitioning from other languages.

Requirements

  • 4+ years of software engineering experience, primarily in backend development with a JVM language.
  • Some commercial experience with Kotlin.
  • Hands-on experience with Spring Boot.
  • Experience building and maintaining REST APIs and distributed systems.
  • Solid SQL knowledge and relational database design experience, 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.

Benefits

  • Service agreement collaboration with independent delivery and invoicing.
  • Work on an AI-native development environment.
  • Opportunity to contribute to a significant backend modernization effort.
  • Exposure to partner-facing ecosystem, internal tools, and AI agentic bot development.

Interested in this position?

Apply directly on the company website

Apply Now

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