Senior C# Engineer – .NET 8/9, AWS Lambda, SQS, SNS – OUTSIDE IR35

Senior C# Engineer – .NET 8/9, AWS Lambda, SQS, SNS – OUTSIDE IR35

£700–£800/day • 100% Remote • 11‑month rolling contract

Takeaway:

Lead the architecture and build of a greenfield SaaS platform as a deeply senior, hands‑on C# engineer, with heavy emphasis on deep .NET engineering, high‑performance distributed systems, and real‑world AWS serverless delivery. You’ll also have the opportunity to develop hands‑on skills with Claude Code, one of the most advanced AI‑assisted development tools in the industry.

Role Overview:

You’ll operate as the technical spearhead for a greenfield product build, reporting to the Director of Engineering. Expect deep backend engineering, distributed system design, and high‑quality serverless delivery, plus the chance to adopt modern AI‑assisted development practices as part of your workflow.

What You’ll Bring:

• Senior/Staff‑level backend mastery in C# and .NET 8/9, with the ability to architect and lead distributed REST microservices at scale.
• Strong authority in AWS serverless engineering: Lambda‑first mindset, hands‑on experience with API Gateway, SQS, Step Functions, EventBridge and IAM.
• Deep data expertise across Aurora MySQL and DynamoDB: schema design, access patterns, indexing, query tuning, and pragmatic trade‑offs around consistency, scale and cost.
• Real‑world experience designing event‑driven systems with SQS: idempotency, retries, ordering, DLQs and operational resilience.
• Strong API design sensibility: versioning, documentation, throttling, backwards compatibility, and a genuine obsession with developer experience.
• Product‑first mindset: comfortable shaping requirements, partnering with BAs, and operating without a traditional PO.
• Excellent communication skills and confidence in ad‑hoc client interaction.
• Rigorous engineering standards: Git‑based workflows, trunk‑based development, CI/CD (GitHub Actions), IaC (CDK/Terraform), comprehensive testing and secure‑by‑default coding.
• Pragmatic, outcome‑oriented, comfortable with ambiguity, and biased toward shipping.

What You’ll Own:

• Architecting, building and shipping complex, high‑performance distributed services in C#/.NET 8/9 on AWS Lambda.
• Designing and delivering resilient event‑driven systems using SQS and related AWS messaging primitives.
• Owning features end‑to‑end: product thinking, scoping, trade‑offs, sequencing and delivery.
• Designing clean, well‑versioned, well‑documented APIs that other engineers love to consume.
• Championing a high‑quality engineering culture: testing discipline, peer review, CI/CD excellence, observability, performance and secure coding.
• Developing hands‑on skills with Claude Code, including AI‑assisted development patterns, smart refactoring, automated context management and productivity‑boosting workflows.

Contract Details:

• £700–£800/day
• Outside IR35
• 100% remote (UK)
• 11‑month rolling contract