Building Resilient .NET APIs for Scale

Reliable APIs are rarely the result of one framework choice. They come from boundaries, observability, and disciplined failure handling.

Start with clear domains

Most API instability starts with unclear ownership. If pricing logic, identity rules, and notifications all mutate the same service layer, releases become fragile. I prefer domain-focused modules with explicit contracts.

app.MapGroup("/orders")
   .WithTags("Orders")
   .MapPost("/", CreateOrderAsync);

That structure keeps routing simple while still allowing each domain to evolve independently.

Make failures visible

Retries are not enough. Production systems need traces, structured logs, and alerting based on business outcomes, not just exception counts.

Cache selectively

Caching improves throughput only when invalidation rules are explicit. For operational dashboards, I usually cache aggregate reads and leave transactional writes uncached.