Middle Java Engineer with Kotlin

We are looking for a Middle Java Engineer with Kotlin to join our team in Poland!

As a Middle Java Engineer, you’ll join client's AI team, where we’re shaping the future of shopping with leading-edge Agentic AI solutions. Together, we’re building intelligent systems that not only enhance the experience for sellers and buyers but also set new standards for innovation - just like the boldest ideas coming out of Silicon Valley. Become part of our dynamic AI R&D environment, where your creativity and engineering skills will drive the next generation of intelligent shopping experiences.

Our California-based client is a global e-commerce company that operates one of the largest and most established online marketplaces. For over 20 years, they have been connecting millions of sellers and buyers across more than 190 countries and territories. Their platform supports a wide range of products - from everyday items to unique and hard-to-find goods 0 and helps individuals and businesses grow by reaching a global audience. The company continues to develop its services with a focus on improving technology, user experience, reliability, and trust.

Responsibilities:

• Design and develop new solutions (approximately 70% greenfield development, 30% optimization and maintenance).
• Implement clean, testable, and efficient services using Kotlin on JDK 17, ensuring interoperability with existing Java components.
• Collaborate closely with Data Science and Machine Learning teams to design and implement LLM-driven workflows.
• Participate in architectural and code reviews across a modern technology stack (Kotlin/Java, Spring Boot 3, Reactor).
• Take ownership of service reliability, including CI/CD pipelines (GitHub Actions) and system observability.
• Work within a Scrum framework (two-week sprints, CET core working hours) in collaboration with product owners based in the US (EDT) and Europe.

Requirements:

• 3+ years of building backend services in Java/Kotlin (and happy to deepen Kotlin).
• Solid Spring ecosystem knowledge (Spring Boot 3, Spring Data, Spring Cloud).
• Hands-on with a NoSQL store (MongoDB, DynamoDB, or Cassandra).
• Familiarity with API styles (REST, gRPC, GraphQL) & distributed design patterns.
• Very good spoken and written English (C1)
• BSc or MSc in Computer Science, Engineering, or a relevant field

Nice to have:

• Kafka
• Docker + Kubernetes
• ETL pipelines
• Vector search / LLM integration.