RESTful API best practices with ASP.NET Core Part 2
Testing, Performance, Security, Microservices & Deployment
Introduction: From Solid Foundations to Production Excellence
In Part 1 of RESTful API Mastery, we established the architectural and technical foundations required to build reliable, evolvable RESTful APIs with ASP.NET Core. However, a well-designed API only becomes truly valuable when it is tested, observable, secure, scalable, and deployable in real-world environments.
This second part focuses on the advanced and operational aspects of RESTful APIs—the areas where enterprise systems typically succeed or fail. These practices are widely adopted across large .NET platforms and cloud-native architectures.
1. API Documentation with Swagger and OpenAPI Standards
Clear documentation is not optional; it is a contract between API teams and consumers.
Enabling OpenAPI in ASP.NET Core
builder.Services.AddSwaggerGen(options =>
{
options.SwaggerDoc("v1", new()
{
Title = "Store API",
Version = "v1"
});
});Enhancing Documentation with XML Comments
<PropertyGroup> <GenerateDocumentationFile>true</GenerateDocumentationFile> </PropertyGroup> /// <summary>Retrieves all available products</summary> [HttpGet] public IActionResult GetProducts() => Ok();
Well-documented APIs reduce onboarding time and prevent integration errors.
2. Testing RESTful APIs: Unit, Integration, and End-to-End
Testing is a first-class engineering discipline, not an afterthought.
Unit Testing Controllers and Services
[Fact]
public void Get_ReturnsOkResult()
{
var controller = new ProductsController();
var result = controller.Get();
Assert.IsType<OkObjectResult>(result);
}Integration Testing with WebApplicationFactory
public class ProductsApiTests : IClassFixture<WebApplicationFactory<Program>>
{
private readonly HttpClient _client;
public ProductsApiTests(WebApplicationFactory<Program> factory)
{
_client = factory.CreateClient();
}
}Comprehensive testing significantly reduces production regressions.
3. Performance Optimization Techniques for ASP.NET Core APIs
Performance optimization starts with measurement, not assumptions.
Asynchronous Programming
[HttpGet]
public async Task<IActionResult> GetAsync()
{
var data = await _repository.GetAsync();
return Ok(data);
}Response Compression
builder.Services.AddResponseCompression(); app.UseResponseCompression();
Combined with caching, compression delivers measurable latency improvements.
4. Real-World Example: Building an E-Commerce REST API
E-commerce APIs require consistency, performance, and transactional safety.
Order Creation Endpoint
[HttpPost]
public async Task<IActionResult> CreateOrder(CreateOrderRequest request)
{
var order = await _orderService.CreateAsync(request);
return CreatedAtAction(nameof(GetOrder), new { id = order.Id }, order);
}Key Considerations
- Idempotency for payment operations
- Versioned contracts
- Audit-friendly logging
5. Microservices Communication Patterns
As systems grow, APIs rarely operate in isolation.
Synchronous HTTP Communication
- Simple to implement
- Easy to debug
- Risk of cascading failures
Resiliency with Polly
services.AddHttpClient("catalog")
.AddTransientHttpErrorPolicy(p =>
p.WaitAndRetryAsync(3, _ => TimeSpan.FromSeconds(2)));Resiliency patterns are mandatory in distributed systems.
6. Monitoring, Logging, and Observability
You cannot operate what you cannot observe.
Structured Logging with ILogger
_logger.LogInformation("Order {OrderId} created", order.Id);Health Checks
builder.Services.AddHealthChecks();
app.MapHealthChecks("/health");Observability is a prerequisite for reliability.
7. Advanced Security Best Practices
Security must be layered and continuously enforced.
HTTPS Enforcement
app.UseHsts(); app.UseHttpsRedirection();
Secure Headers and Validation
- Validate all inputs
- Sanitize outputs
- Apply least-privilege authorization
Security failures are rarely caused by frameworks—but by configuration gaps.
8. Deployment Strategies for ASP.NET Core APIs
Deployment is part of API design.
Containerization with Docker
FROM mcr.microsoft.com/dotnet/aspnet:8.0 WORKDIR /app COPY . . ENTRYPOINT ["dotnet", "Store.Api.dll"]
Cloud-Native Readiness
- Stateless services
- Externalized configuration
- Zero-downtime deployments
9. API Gateway Integration Patterns
API gateways centralize cross-cutting concerns.
Common Responsibilities
- Authentication and authorization
- Rate limiting
- Request routing
Popular choices include Azure API Management and YARP.
10. Future Trends and Evolving REST Best Practices
REST continues to evolve alongside the .NET ecosystem.
Emerging Trends
- Hybrid REST + gRPC architectures
- Increased use of API gateways
- Contract-first development
Forward-looking APIs embrace evolution without sacrificing stability.
Final Conclusion: RESTful API Mastery in ASP.NET Core
With both parts combined, you now have a complete, enterprise-grade guide to building RESTful APIs with ASP.NET Core.
True mastery comes from discipline, consistency, and operational awareness. When APIs are treated as long-lived products and engineered accordingly, they become powerful enablers for scalable and secure systems.
REST is not outdated—it is refined. And ASP.NET Core remains one of the most capable platforms to implement it correctly.
If this article helped you, consider supporting my work.
☕ Buy me a coffee