> Markdown version of [/jobs/ext/3435794-backend-developers](https://www.wearedevelopers.com/jobs/ext/3435794-backend-developers). Every page supports `.md` or `Accept: text/markdown`. Links point to the HTML versions so they work for humans too. Agent guide: [/agents.md](https://www.wearedevelopers.com/agents.md).

---

# Backend Developers

- **Company:** Postaladdress
- **Location:** Spain (Remote available)
- **Contract:** Permanent contract
- **Skills:** Java (Programming Language), JavaScript (Programming Language), Artificial Intelligence, C Sharp (Programming Language), Code Coverage, Code Review, Software Debugging, Junit, Python (Programming Language), Software Engineering, TypeScript, Backend, Xunit, Pytest, Integration Tests, Code Restructuring, Golang
- **Published:** September 5, 2026
- **Apply:** https://startup.jobs/backend-developer-ai-trainer-spain-anyone-ai-8825658

## About the Role

* Advanced professional written proficiency in English
 * 3-7 years of professional software engineering experience
 * Strong proficiency in Python and JavaScript/TypeScript; working knowledge of Java, C#, or Go
 * Backend or full-stack development experience in production systems
 * Experience with testing frameworks (e.g., pytest, Jest, JUnit, xUnit, Go testing)
 * Proven ability to debug and navigate large, multi-file codebases
 * Experience with code reviews, refactoring, and production migrations

Engagement: Part-time, project-based expert evaluation work

## Description

Contributors will design and evaluate realistic software engineering tasks, including bug resolution, feature implementation, refactoring/migration, and test generation. Work includes both creating complex coding scenarios and reviewing peer submissions for quality and accuracy., Contributors will:

 * Design and implement multi-file coding tasks across bug fixing, feature development, refactoring, and testing
 * Write clear natural-language specifications and reference implementations
 * Develop and extend unit and integration test suites
 * Review peer-generated tasks for correctness, clarity, and realism
 * Identify edge cases, ambiguities, and potential failure modes
 * Ensure alignment between specifications, code, and expected outputs

Expected Outcomes:

 * High-quality, production-realistic coding tasks
 * Complete and correct reference implementations
 * Robust test coverage and validation artifacts
 * Structured, actionable peer review feedback