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Backend Developer (Java)

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Onsite

Backend Developer (Java)

Rakuten Viber

Backend Developer (Java)

Skills

MongoDBDockerPythonJavaMicroservicesAIKubernetesJavascript

2 months ago

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Important information


Contract type:

Permanent

Location:

Warsaw, Poland

Work mode:

Onsite

Published on:

7 August 2026

What they need


Rakuten Viber is one of the most popular and downloaded apps in the world. Working with us provides a unique opportunity to influence hundreds of millions of our users and to be part of the journey that makes us a super-app. Our mission is to make people’s lives easier by enabling meaningful connections, from precious moments with family and friends, through managing business relationships to pursuing their passions.

We are a global team of engineers dedicated to creating the best tools to ensure safe, convenient, and fun communication for millions of users worldwide. Our culture is built on innovation, teamwork, and a commitment to excellence. We offer a unique opportunity to work with cutting-edge technologies, including microservices architecture, and influence the lives of millions of people.

As a Backend Developer at Viber, you will be involved in developing and maintaining high-traffic with over 1 billion messages a day and dozens of scalable services, ensuring the fast and reliable operation of our platform. Your tasks will include developing new features, optimizing performance, ensuring data security, and solving complex technical challenges within our microservices architecture, using a combination of Java, along with non-blocking and reactive approaches, Cloud services, and NoSQL databases.

Responsibilities:

  • Planning, designing, developing and maintaining Java high-availability applications that can be high-volume and low-latency.
  • Define application objectives and functionality.
  • Ensure application designs conform with business goals.
  • Support continuous improvement, investigating alternatives and technologies, and presenting for architectural review.
  • Work in a highly motivated team, closely with Product and Architects teams on large mission-critical systems.

Requirements:

  • At least 4 years of experience as a Backend Developer, with at least 2 years in Java.
  • Advanced knowledge of Java, from frameworks to libraries. Experience in Async and/or reactive Java frameworks (such as Vertx, Rxjava, Akka).
  • Advanced knowledge of unit testing frameworks and mocking.
  • Knowledge of cloud technologies.
  • Experience with using AI tools to increase productivity and quality.
  • Experience with large scale NoSQL database (such as Couchbase, MongoDB).
  • Experience with microservices development based on Docker and Kubernetes.
  • Experience with Agile methodology.
  • Striving for new knowledge and skill improvement.
  • Fluent in written and spoken English (interviews are in English).
  • Excellent oral and written communication skills.
  • Higher technical education.

Advantages:

  • Knowledge of Javascript and web ui technologies
  • Experience with other server-side languages such as Python.
  • Experience working with remote teams.

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