Senior Dotnet Developer

About the role

We are hiring a Senior .NET Commerce Integration Engineer to build and run the APIs that connect our retail mobile app to SAP Commerce Cloud ( e-commerce platform) and to ERP, order management and warehouse systems. You will own the middleware layer: secure APIs, Azure API Management policies, real-time order and inventory sync, and the reliability patterns that keep a customer-facing app fast during peak trading.

• Location: Remote / hybrid (to be confirmed by client)
• Type: Full-time or contract
• Experience: 6–10 years in backend development, at least 3 in integration-heavy roles
• Reports to: Integration / Solution Architect

Key responsibilities

1. Build and maintain backend APIs in .NET 8/9 (ASP.NET Core) that serve the POQ mobile app: product catalogue, pricing, basket, checkout, customer account, loyalty and order history, built on SAP Commerce OCC REST APIs.
2. Design real-time commerce integrations that sync orders, inventory and stock availability between SAP Commerce Cloud, ERP/OMS and the warehouse system (WMS), using event-driven patterns (Azure Service Bus, Event Grid, Functions, webhooks).
3. Own Azure API Management (APIM): write and maintain policies for JWT validation, rate limiting and quotas, caching, request/response transformation, CORS, IP filtering, backend routing and retries.
4. Secure the platform: validate JWT/OAuth 2.0 / OpenID Connect tokens server-side (signature, issuer, audience, expiry, key rotation via JWKS), and keep all secrets in Azure Key Vault accessed through Managed Identity.
5. Engineer for failure: implement timeouts, retries with exponential backoff and jitter, circuit breakers, rate-limit handling (HTTP 429 / Retry-After) and dead-letter queues using Polly / Microsoft.Extensions.Resilience.
6. Guarantee data integrity: make sync processes idempotent (idempotency keys, upserts, de-duplication, outbox pattern) so duplicate or out-of-order messages never create double orders or wrong stock.
7. Optimise performance: call independent downstream APIs in parallel (async/await, Task.WhenAll), manage HttpClient correctly via IHttpClientFactory / typed clients, and keep mobile response times low.
8. Accelerate delivery with code generation: generate API clients and models from OpenAPI/Swagger specs (NSwag, Kiota, AutoRest, Refit) rather than hand-writing them.
9. Modernise legacy code: support existing .NET Framework 4.8 services and plan their migration to modern .NET.
10. Operate what you build: monitoring and alerting with Application Insights / Azure Monitor, CI/CD with Azure DevOps or GitHub Actions, and production support during peak trading.