Introduction

ASP.NET Core applications can experience slow response times, excessive memory consumption, and thread exhaustion due to inefficient request handling, incorrect service lifetimes, and improper async patterns. Common pitfalls include singleton dependencies holding excessive memory, middleware executing in an incorrect order, and async methods blocking threads. These issues become particularly critical in high-traffic enterprise applications where performance, scalability, and resource efficiency are essential. This article explores advanced ASP.NET Core troubleshooting techniques, optimization strategies, and best practices.

Common Causes of ASP.NET Core Issues

1. Slow API Responses Due to Inefficient Dependency Injection

Incorrect service lifetimes cause performance degradation.

Problematic Scenario

// Injecting a scoped service into a singleton
public class MySingletonService
{
    private readonly IScopedService _scopedService;
    public MySingletonService(IScopedService scopedService)
    {
        _scopedService = scopedService;
    }
}

Injecting a `Scoped` service into a `Singleton` causes inconsistent behavior.

Solution: Correct Dependency Lifetimes

// Use appropriate service lifetimes
services.AddSingleton();
services.AddScoped();

Ensuring correct dependency lifetimes prevents unintended memory leaks.

2. Memory Leaks Due to Improper Middleware Execution

Incorrect middleware order can cause unhandled requests to leak resources.

Problematic Scenario

// Incorrect middleware order
app.UseRouting();
app.UseAuthentication();
app.UseAuthorization();

Placing `UseAuthentication` after `UseRouting` may cause unauthenticated requests to reach handlers.

Solution: Ensure Proper Middleware Ordering

// Correct middleware order
app.UseRouting();
app.UseAuthentication();
app.UseAuthorization();
app.UseEndpoints(endpoints => { endpoints.MapControllers(); });

Ordering middleware correctly ensures authentication and authorization checks execute before reaching endpoints.

3. Thread Starvation Due to Improper Async Handling

Blocking async calls causes thread pool exhaustion.

Problematic Scenario

// Blocking async operation
public IActionResult GetData()
{
    var data = GetDataAsync().Result;
    return Ok(data);
}

Using `.Result` blocks the request thread, leading to performance issues.

Solution: Use Async/Await Properly

// Correct async method
public async Task GetData()
{
    var data = await GetDataAsync();
    return Ok(data);
}

Using `await` prevents unnecessary thread blocking.

4. High CPU Usage Due to Inefficient Logging

Excessive logging slows down application performance.

Problematic Scenario

// Excessive synchronous logging
logger.LogInformation("Processing request for user {UserId}", userId);

Logging large amounts of data synchronously can impact performance.

Solution: Use Buffered Logging

// Configure logging to use buffering
services.AddLogging(logging =>
{
    logging.AddConsole(options => options.IncludeScopes = false);
    logging.AddDebug();
});

Using buffered or batched logging minimizes CPU overhead.

5. Request Timeouts Due to Improper HTTP Client Usage

Reusing `HttpClient` incorrectly can lead to socket exhaustion.

Problematic Scenario

// Creating HttpClient instances in every request
public async Task FetchData()
{
    using (var client = new HttpClient())
    {
        return await client.GetStringAsync("https://api.example.com/data");
    }
}

Creating a new `HttpClient` for each request causes connection issues.

Solution: Use `HttpClientFactory`

// Register and use HttpClientFactory
services.AddHttpClient();
public class ApiService
{
    private readonly HttpClient _httpClient;
    public ApiService(HttpClient httpClient)
    {
        _httpClient = httpClient;
    }
    public async Task FetchData()
    {
        return await _httpClient.GetStringAsync("https://api.example.com/data");
    }
}

Using `HttpClientFactory` efficiently manages HTTP connections and prevents socket exhaustion.

Best Practices for Optimizing ASP.NET Core Applications

1. Optimize Dependency Injection

Ensure proper service lifetimes (`Singleton`, `Scoped`, `Transient`) to avoid performance issues.

2. Configure Middleware Correctly

Place authentication and authorization middleware before endpoint execution.

3. Avoid Blocking Async Calls

Use `async/await` to prevent request thread starvation.

4. Use Efficient Logging Strategies

Minimize excessive logging and use structured, batched logs.

5. Manage HTTP Clients Properly

Use `HttpClientFactory` to optimize network connections and prevent socket exhaustion.

Conclusion

ASP.NET Core applications can suffer from slow responses, memory leaks, and threading issues due to inefficient dependency injection, misconfigured middleware, and improper async execution. By structuring middleware correctly, optimizing dependency injection, following async best practices, improving logging efficiency, and managing HTTP clients properly, developers can build high-performance and scalable ASP.NET Core applications. Regular monitoring using Application Insights and performance profiling with .NET diagnostics tools helps detect and resolve performance issues proactively.