Senior Backend Engineer (C#) - AI Data Platform

Senior Backend Engineer (C#) — AI Data Platform

What if your C# expertise could directly shape the infrastructure powering the next generation of AI? We're looking for a Senior Backend Engineer to build and optimize the data pipelines, annotation tooling, and evaluation systems that leading AI labs depend on to train and benchmark frontier models.

This is a fully remote, flexible contract role for an experienced engineer who wants to work on genuinely hard problems at the intersection of software engineering and AI research — without the constraints of a full-time role.

• Organization:
  Alignerr
• Type:
  Hourly Contract
• Location:
  
  Remote
• Commitment: 20–40 hours/week

• Design, build, and optimize high-performance backend systems in C# that power AI data pipelines and evaluation workflows
• Develop backend services and tooling for large-scale data annotation, validation, and quality control
• Build and maintain RESTful APIs and RPC services for reliable inter-service communication
• Integrate with cloud-native data services and orchestrate workflows across message bus architectures
• Improve reliability, performance, and safety across existing production C# codebases
• Collaborate with data, research, and engineering teams to support model training and evaluation workflows
• Identify bottlenecks and edge cases in system behavior and implement scalable, maintainable fixes
• Participate in synchronous design reviews to iterate on system architecture and implementation decisions

• 5+ years of professional experience building scalable backend services in C#
• Strong systems programming background with a deep understanding of performance and reliability trade-offs
• Mastery of modern frameworks for building RESTful APIs and RPC services
• Solid experience integrating with cloud-native data services and message bus architectures
• Native or fluent English speaker with clear written and verbal communication skills
• Self-directed and dependable — you can commit 20–40 hours per week and deliver without hand-holding

• Prior experience with data annotation, data quality pipelines, or model evaluation systems
• Familiarity with AI/ML workflows, model training, or benchmarking infrastructure
• Experience with distributed systems design or developer tooling
• Background in full-stack development alongside strong backend fundamentals

• Work on real production systems used by leading AI research labs — this is high-impact engineering, not toy projects
• Fully remote and async-friendly — work when and where you do your best thinking
• Freelance autonomy with the structure of meaningful, ongoing technical work
• Collaborate with engineers and researchers at the cutting edge of AI development
• Potential for ongoing contract extension as projects scale and new work launches