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
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