[8BE] Senior Backend Engineer

Job Description
We’re building the backend of a white-label B2B e-commerce platform for a leading US promotional products company. The platform powers multiple branded Shopify Plus storefronts. It runs on a fully decoupled microservices architecture on AWS covering Identity, Profile, Order Management, Inventory, Pricing, Catalog, and Marketplace integrations. The existing legacy services stay supported while the migration happens.
What you’ll do:
• Design and build scalable RESTful microservices with ASP.NET Core Web API (.NET 8) and CQRS
• Own core services: Order Management, Inventory, Pricing Engine, Catalog Sync, and Notifications
• Build and consume Shopify Webhooks and REST/GraphQL APIs (Storefront API, Admin API)
• Integrate with external systems such as Amazon SP-API, Walmart Marketplace API, ERP, payment gateways, and tax services
• Work with legacy services where the migration is phased or partial
• Write unit, integration, and BDD tests (xUnit, Reqnroll, FluentAssertions)
• Define API contracts and inter-service communication (SQS, EventBridge) with the Team Lead
• Take part in code reviews and architecture decisions, and help hold the engineering standard
• Support environment setup and infrastructure-as-code with DevOps on AWS
• Join sprint planning, stand-ups, and technical discussions with the client

Qualifications
Must have:
• 4+ years of backend development with strong C# / .NET (ASP.NET Core, .NET 6+)
• Solid grasp of clean architecture: DDD, CQRS, repository pattern, dependency injection
• Experience building and integrating REST APIs, including OpenAPI / Swagger
• Working knowledge of AWS: Lambda, SQS, S3, RDS or DynamoDB
• Relational (PostgreSQL or SQL Server) and NoSQL (MongoDB) databases
• JWT / OAuth 2.0 authentication
• Brownfield experience: plugging new services into existing systems
• Docker and containerized workflows
• Strong written and spoken English
• Agile/Scrum with Jira
Nice to have:
• Retail, e-commerce, or B2B commerce experience (catalogs, pricing engines, cart/checkout, marketplace integrations)
• Marketplace API integrations (Amazon SP-API, Walmart)
• Event-driven architecture (EventBridge, RabbitMQ)
• Keycloak and multi-realm identity management
• EF Core with Npgsql
• Promotional products or print-on-demand domain knowledge