SAFE EVEN WHEN THE REQUEST REPEATS.

An e-commerce backend designed around checkout, payments, inventory workflows and safe handling of repeated operations, built on ASP.NET Core with Clean Architecture and CQRS.

1. 01 / SECTION

   THE PROBLEM

   Checkout and payment workflows receive retried commands and duplicate webhooks when networks fail or clients retry.

   Without protection, a single customer action can charge twice, decrement stock twice, or create duplicate orders.

2. 02 / SECTION

   THE APPROACH

   Idempotency keys ensure operations process once; subsequent requests safely return the stored result without re-triggering side effects.

   Commands and queries are separated with CQRS through MediatR, so write paths stay explicit about the state they change.

3. 03 / SECTION

   STRUCTURE

   Clean Architecture keeps domain rules independent of ASP.NET Core and EF Core, with the domain model owning invariants around carts, orders and inventory.

   JWT-based authentication protects the API surface, and Redis backs caching and fast lookups on hot read paths.

4. 04 / SECTION

   OUTCOME

   Repeated checkout attempts and duplicate payment webhooks converge on a single correct result.

   The backend stays predictable under retry-heavy, real-world network conditions instead of only on the happy path.