Senior Backend Developer - Java or Python

Senior Backend Developer

• Java or Python Key Details: Rate: up to 130 PLN/h net + VAT Work model: Hybrid (3 days a week from the office) Location: Warsaw, Gdańsk, or Gdynia Contract type: B2B agreement (signed directly with Optiveum) About the role: We are Optiveum, and we are currently looking for a Senior Backend Developer (Java or Python) to join our client's dynamic team. In this role, you will contribute to the ongoing development of the Automated Security Retest Engine, a cutting-edge security retesting platform that automates the analysis of security assessment reports and the verification of remediation actions. The project involves developing and maintaining a Python-based processing pipeline as well as a Java Spring Boot web application that provides the user interface.

Your responsibilities

Designing and implementing new features for the platform. Integrating external tools and APIs. Improving the reliability and quality of generated tests and analysis. Writing automated tests, investigating defects, and maintaining technical documentation. Collaborating with security and product stakeholders to translate requirements into practical, maintainable software.

Ensuring security as a core requirement: preserving target-scope restrictions, protecting credentials and user data, validating inputs, and providing reliable evidence for retest outcomes. Must-have knowledge and experience: Professional software development experience in Python and/or Java. Experience in developing and maintaining backend applications and REST APIs.

For Java: familiarity with Spring Boot and common application-development practices. For Python: familiarity with modular application design, dependency management, and automated testing. Proven experience writing and maintaining automated tests. Working knowledge of Git and collaborative software-development workflows (including code reviews).

Understanding of secure software development (input validation, authentication, authorization, safe handling of secrets). Ability to analyze an existing codebase, troubleshoot issues, and deliver changes with appropriate documentation. Good written and spoken English for technical communication. Nice-to-have knowledge and experience: Experience with both Python AND Java/Spring Boot.

Experience integrating LLM APIs or building LLM-assisted workflows (including structured-output validation and error handling). Familiarity with application security testing, especially DAST and SAST. Experience with tools such as OWASP ZAP, Nuclei, Semgrep, pytest, or security-test automation. Experience with PDF processing, OCR, or document extraction.

Familiarity with web technologies (JavaScript, HTML, CSS, Bootstrap, Thymeleaf). Experience with SQL databases, Maven, CI/CD, Docker, or cloud services. Interest in application security, vulnerability remediation, and security engineering.

What we offer

B2B agreement with Optiveum as your contracting party. Transparent working conditions. Ongoing support from the Optiveum team throughout our cooperation. The opportunity to work in an international, highly collaborative environment.