Back End Developer (AI Infrastructure)

About The Role What if the code you write could directly power the AI systems shaping how millions of people interact with technology? We're looking for Back End Developers in Madrid to design, build, and optimize the server-side systems and APIs that drive cutting-edge AI products — from data pipelines and model-serving infrastructure to scalable microservices that handle real-world traffic at scale.

This is a fully remote, flexible contract role. Whether you're a seasoned engineer looking for meaningful project work or a strong developer ready to apply your skills to AI-adjacent infrastructure, this is your chance to build things that matter.

• Organization: Alignerr
• Type: Hourly Contract
• Location: Remote
• Commitment: 10–40 hours/week

What You'll Do

• Design, develop, and maintain robust back end services, APIs, and data pipelines
• Build scalable, high-performance server-side architecture to support AI training and inference workloads
• Write clean, well-documented, and testable code following engineering best practices
• Integrate with databases, message queues, cloud services, and third-party APIs
• Optimize system performance, reliability, and scalability as usage grows
• Collaborate asynchronously with distributed teams of engineers, researchers, and product leads
• Troubleshoot production issues, conduct code reviews, and contribute to architectural decisions
• Work independently on task-based and project-based assignments on your own schedule

Who You Are

• Proficient in one or more back end languages — Python, Go, Java, Node.js, Rust, or similar
• Solid understanding of RESTful API design, microservices architecture, and distributed systems
• Experienced with relational and/or NoSQL databases (PostgreSQL, MongoDB, Redis, etc.)
• Comfortable working with cloud platforms such as AWS, GCP, or Azure
• Familiar with version control (Git), CI/CD pipelines, and containerization (Docker, Kubernetes)
• Strong problem-solving skills and the ability to debug complex systems independently
• Self-motivated, reliable, and effective when working asynchronously without close supervision
• Clear communicator who can document decisions and collaborate across time zones

Nice to Have

• Experience building infrastructure for machine learning or AI systems
• Familiarity with data processing frameworks (Apache Kafka, Spark, Airflow, or similar)
• Background in performance optimization, caching strategies, or high-throughput systems
• Knowledge of authentication, authorization, and security best practices
• Experience with serverless architectures or event-driven design patterns
• Contributions to open-source projects or a strong portfolio of personal/professional work

Why Join Us

• Work on cutting-edge AI infrastructure projects alongside leading research labs
• Fully remote and flexible — set your own hours and work from anywhere
• Freelance autonomy with access to meaningful, technically challenging work
• Build systems at the intersection of software engineering and artificial intelligence
• Collaborate with a global network of talented engineers and researchers
• Potential for ongoing work and contract extension as new projects launch