Job Description
Senior C# Engineer .Net, Typescript, Lambda, API Gateway, SQS, SNS, Cognito? £700 £800 per day Outside IR35100% Remote8-month rolling contractPlay a pivotal role in architecting and delivering a major greenfield B2B SaaS platform as a senior, hands-on, backend C# engineer. Expect serious backend engineering, high-performance event driven systems, and production grade AWS serverless delivery with an elevated focus on API engineering , identity & access , and secure-by-default service design . Youll also gain hands-on experience with Claude Code and modern agentic development workflows.
Role Overview:
Youll act as the technical spearhead for a greenfield product build, reporting to the Director of Engineering and working closely with their IAM Technical Lead. In addition to deep backend C#, API engineering and AWS skills, without being a security expert, youll ideally have some experience of AWS Cognito, AWS IAM and some Typescript.
What Youll Bring: Senior/Staff-level backend mastery in C# and .NET 9/10 , capable of architecting and leading distributed REST microservices at scale.
Advanced AWS serverless expertise including Lambda, API Gateway , SQS, SNS, Step Functions & EventBridge .Serious API engineering capability : versioning, documentation, throttling, rate-limiting, contract stability, DX-first design, and building APIs that other engineers love to consume.
Some frontend experience with Typescript will be advantageousSome real-world identity engineering: familiarity with AWS IAM , permission modelling, least-privilege design, cross-service auth patterns, and secure-by-default access controls.
Some Hands-on experience with AWS Cognito : user pools, identity pools, OAuth2/OIDC flows, JWT validation, token lifecycles, and integrating Cognito-backed auth into API Gateway and Lambda.
Data expertise across Aurora MySQL and DynamoDB: schema design, access patterns, indexing, query tuning, and pragmatic trade-offs around consistency, scale and cost.
Event-driven architecture experience with SQS: idempotency, retries, ordering, DLQs, and operational resilience.
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.
High engineering standards : Git-based workflows, trunk-based development, CI/CD (GitHub Actions), IaC (CDK/Terraform), comprehensive testing, and secure-by-default coding.
Outcome-oriented pragmatism : comfortable with ambiguity and biased toward shipping.
What Youll Own: Architecting, building and shipping high-performance event driven services in C#/.NET 9/10 on AWS Lambda.
Designing secure, scalable API architectures using API Gateway, IAM, Cognito, and modern identity patterns.
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.
Championing engineering excellence : testing discipline, peer review, CI/CD quality, observability, performance and secure coding.
Developing hands-on skills with Claude Code : agentic workflows, smart refactoring, automated context management, and productivity-boosting AI patterns.
Contract Details:£700£800/dayOutside IR35100% Remote (UK only)8-month rolling contract
Senior C# Engineer Typescript, Lambda, API Gateway, SQS, SNS in London employer: Smart Sourcer Limited
Join a forward-thinking company at the forefront of the data centre construction revolution, where your role as a Project Manager will be pivotal in shaping the future of AI. With a strong emphasis on employee growth and a collaborative work culture, you will have access to comprehensive training and development opportunities while working in vibrant locations like Central London and High Wycombe. Enjoy competitive remuneration and benefits, all while contributing to high-impact projects that drive innovation in engineering and infrastructure.
