Understanding the Problem

Performance degradation in ASP.NET Core applications is often caused by excessive middleware processing, inefficient scoped service usage, or unoptimized database interactions. These issues lead to increased server load, slow responses, and degraded user experience.

Root Causes

1. Middleware Overhead

Including too many middleware components or misplacing them in the pipeline increases response latency.

2. Inefficient Dependency Injection

Misconfigured dependency lifetimes, such as overusing scoped services, cause unnecessary object creation and memory usage.

3. Unoptimized Database Queries

Slow or redundant database queries result in delayed API responses and high server resource usage.

4. Blocking Async Operations

Blocking asynchronous calls with .Result or .Wait() reduces scalability by blocking threads.

5. Inefficient Caching

Failing to implement proper caching for repeated requests increases server load and slows down responses.

Diagnosing the Problem

ASP.NET Core provides various tools and techniques to diagnose performance bottlenecks. Use the following methods:

Enable Logging

Configure logging to capture detailed request and middleware execution data:

builder.Logging.AddConsole(options => {
    options.IncludeScopes = true;
    options.TimestampFormat = "[yyyy-MM-dd HH:mm:ss] ";
});

Profile Middleware Execution

Use the built-in diagnostics to track middleware performance:

app.Use(async (context, next) => {
    var stopwatch = Stopwatch.StartNew();
    await next.Invoke();
    stopwatch.Stop();
    Console.WriteLine($"Middleware execution time: {stopwatch.ElapsedMilliseconds} ms");
});

Analyze Dependency Injection

Inspect registered services and their lifetimes using services.Where():

foreach (var service in builder.Services) {
    Console.WriteLine($"Service: {service.ServiceType}, Lifetime: {service.Lifetime}");
}

Profile Database Queries

Enable database query logging in Entity Framework Core:

optionsBuilder.LogTo(Console.WriteLine, LogLevel.Information);

Monitor Performance Metrics

Use dotnet-counters to monitor CPU and memory usage:

dotnet-counters monitor --process-id 

Solutions

1. Optimize Middleware Usage

Place middleware in the correct order and remove unnecessary components:

app.UseRouting();
app.UseAuthentication();
app.UseAuthorization();
app.UseEndpoints(endpoints => {
    endpoints.MapControllers();
});

Avoid duplicating functionality across middleware components.

2. Configure Dependency Injection Properly

Use appropriate lifetimes for services:

builder.Services.AddSingleton();
builder.Services.AddScoped();
builder.Services.AddTransient();

Avoid injecting scoped services into singletons to prevent runtime errors.

3. Optimize Database Queries

Use efficient queries and avoid fetching unnecessary data:

// Use projections to fetch only required fields
var users = context.Users.Select(u => new { u.Id, u.Name }).ToList();

// Use AsNoTracking for read-only operations
var readOnlyData = context.Users.AsNoTracking().ToList();

4. Avoid Blocking Async Calls

Replace blocking calls with proper async/await patterns:

// Avoid
var result = GetDataAsync().Result;

// Use async/await
var result = await GetDataAsync();

5. Implement Caching

Use in-memory caching to store frequently accessed data:

builder.Services.AddMemoryCache();

app.Use(async (context, next) => {
    var cache = context.RequestServices.GetService();
    if (!cache.TryGetValue("key", out var value)) {
        value = "cached value";
        cache.Set("key", value, TimeSpan.FromMinutes(5));
    }
    await next.Invoke();
});

For distributed environments, use a distributed cache like Redis:

builder.Services.AddStackExchangeRedisCache(options => {
    options.Configuration = "localhost:6379";
});

Conclusion

High CPU usage and slow API responses in ASP.NET Core applications can be resolved by optimizing middleware, configuring dependency injection properly, and improving database queries. By leveraging built-in tools and best practices, developers can create scalable and efficient web applications.

FAQ

Q1: How can I identify slow middleware in my ASP.NET Core application? A1: Use custom logging or diagnostics to measure the execution time of middleware components.

Q2: What is the best way to handle dependency injection in ASP.NET Core? A2: Use appropriate service lifetimes (e.g., Singleton, Scoped, Transient) and avoid injecting scoped services into singletons.

Q3: How do I optimize database performance in Entity Framework Core? A3: Use AsNoTracking for read-only queries, projections to fetch only required fields, and indexes to improve query performance.

Q4: How can I avoid blocking the thread in async operations? A4: Use async/await patterns instead of blocking calls like .Result or .Wait().

Q5: What caching strategies are available in ASP.NET Core? A5: Use in-memory caching for single-instance deployments and distributed caching (e.g., Redis) for multi-instance or cloud-based environments.