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.