Java Backend Engineer — High-Volume Microservices (Hybrid)

Rakuten Viber; Warszawa; Hybrid; PLN 180,000 - 320,000; Full time

Job summary

Rakuten Viber, Warsaw-based, is seeking a Backend Developer to build and maintain high-traffic Java services. You will design scalable, low-latency systems, work on microservices in a cloud environment, and ensure security and performance across a billion daily messages.

The role requires 4+ years in backend development, strong Java expertise, and experience with Docker/Kubernetes, NoSQL databases and Agile practices. Hybrid work is available with in-office presence required several days a week.

Qualifications

• At least 4 years of Backend Development experience with Java.
• Experience with Async/Reactive Java frameworks (e.g., Vert.x, RxJava, Akka).
• Experience with NoSQL databases (e.g., Couchbase, MongoDB).
• Hands-on with Docker and Kubernetes in microservices.
• Knowledge of cloud technologies.
• Experience with unit testing and mocking frameworks.
• Familiarity with Agile methodologies.
• Fluent in written and spoken English.

Responsibilities

• Plan, design, and develop Java high-availability, low-latency applications.
• Define objectives and functionality for services.
• Ensure designs align with business goals and architecture.
• Contribute to architectural reviews and continuous improvement.
• Collaborate with Product and Architects on mission-critical systems.

Skills

Java

Async/Reactive Java

NoSQL databases

Docker & Kubernetes

Cloud technologies

Unit testing

Agile methodologies

English communication

AI tools for productivity

Microservices

Education

Higher technical education

Job description

Rakuten Viber, Warsaw-based, is seeking a Backend Developer to build and maintain high-traffic Java services. You will design scalable, low-latency systems, work on microservices in a cloud environment, and ensure security and performance across a billion daily messages.

The role requires 4+ years in backend development, strong Java expertise, and experience with Docker/Kubernetes, NoSQL databases and Agile practices. Hybrid work is available with in-office presence required several days a week.