Build High-Performance APIs with .NET Minimal API

Introduction

Building fast, scalable, and maintainable APIs is a key requirement for modern applications. With the evolution of .NET, Microsoft introduced Minimal APIs to simplify API development while improving performance. Minimal APIs reduce boilerplate code, improve startup time, and allow developers to focus on business logic instead of framework complexity. This article explains modern approaches to building high-performance APIs using Minimal API architecture in .NET, written in simple words and practical examples.

What Are Minimal APIs in .NET?

Minimal APIs are a lightweight way to build HTTP APIs using ASP.NET Core without the traditional controller-based structure. Instead of controllers, attributes, and multiple files, Minimal APIs allow you to define routes and handlers directly in Program.cs.

Minimal APIs

• Reduce code complexity

• Improve startup performance

• Are ideal for microservices and small-to-medium APIs

• Work well with modern cloud-native architectures

Simple Minimal API Example

var builder = WebApplication.CreateBuilder(args);
var app = builder.Build();

app.MapGet("/hello", () => "Hello from Minimal API");

app.Run();

This creates a fully working API with just a few lines of code.

Why Minimal APIs Are High-Performance

Minimal APIs avoid unnecessary layers such as controllers, filters, and reflection-heavy pipelines. This results in:

• Faster application startup

• Lower memory usage

• Reduced request processing overhead

• Better performance under high load

They are especially useful for APIs that need to handle large numbers of requests with minimal latency.

Modern Design Principles for Minimal APIs

Keep Endpoints Focused and Small

Each endpoint should handle a single responsibility. Smaller endpoints are easier to optimize, test, and scale.

app.MapGet("/users/{id}", (int id) => Results.Ok(new { Id = id, Name = "John" }));

Use Typed Results for Better Performance

Typed results reduce runtime overhead and improve API clarity.

app.MapGet("/status", () => Results.Ok("Service is running"));

Dependency Injection in Minimal APIs

Minimal APIs fully support dependency injection. Services can be injected directly into endpoint handlers.

app.MapGet("/time", (ITimeService service) => service.GetTime());

This keeps code clean and improves testability.

Input Validation and Model Binding

Minimal APIs support automatic model binding from route values, query strings, headers, and request bodies.

app.MapPost("/products", (Product product) =>
{
    if (string.IsNullOrEmpty(product.Name))
        return Results.BadRequest("Name is required");

    return Results.Created($"/products/{product.Id}", product);
});

For larger projects, libraries like FluentValidation can be used.

Use Asynchronous Programming Everywhere

Async and await improve scalability by freeing threads during I/O operations.

app.MapGet("/data", async () =>
{
    await Task.Delay(100);
    return Results.Ok("Async response");
});

Async APIs handle more concurrent users with fewer resources.

Efficient Data Access

Use lightweight ORMs like Dapper or optimized Entity Framework Core queries.

app.MapGet("/orders", async (IDbConnection db) =>
    await db.QueryAsync<Order>("SELECT * FROM Orders")
);

Efficient queries significantly improve API performance.

Caching for Performance Optimization

Caching reduces database calls and improves response time.

app.MapGet("/cached-data", async (IMemoryCache cache) =>
{
    return await cache.GetOrCreateAsync("key", entry =>
    {
        entry.AbsoluteExpirationRelativeToNow = TimeSpan.FromMinutes(5);
        return Task.FromResult("Cached Result");
    });
});

Use Middleware Carefully

Minimal APIs still support middleware, but only add what is necessary.

app.UseHttpsRedirection();
app.UseAuthorization();

Avoid heavy middleware that impacts request performance.

Security Best Practices

Minimal APIs support authentication and authorization.

app.MapGet("/secure", () => "Secure Data")
   .RequireAuthorization();

Use JWT, OAuth, or API keys depending on your use case.

Observability and Logging

Use structured logging and minimal logging levels in production.

app.MapGet("/health", (ILogger<Program> logger) =>
{
    logger.LogInformation("Health check called");
    return Results.Ok("Healthy");
});

When to Choose Minimal APIs

Minimal APIs are ideal for:

• Microservices

• High-performance REST APIs

• Cloud-native applications

• Serverless workloads

• API gateways

For very large enterprise applications with complex MVC needs, controllers may still be suitable.

Minimal API vs Controller-Based API Comparison

Minimal APIs and controller-based APIs both belong to ASP.NET Core, but they serve different architectural needs.

Minimal APIs remove unnecessary abstraction layers, which makes them faster and easier to maintain for modern API-first systems.

Benchmark-Style Performance Explanation

In performance testing scenarios, Minimal APIs consistently show lower latency and reduced memory usage compared to controller-based APIs. Because Minimal APIs skip the MVC pipeline, request handling becomes faster. For example, when handling thousands of concurrent requests, Minimal APIs often show faster response times and lower CPU consumption. This makes them ideal for high-traffic systems such as public APIs, gateways, and real-time services.

Real-World Production Examples

Microservices Architecture

In a microservices-based system, each service focuses on a small domain. Minimal APIs are perfect here because they are lightweight, fast to start, and easy to deploy independently. Teams often use Minimal APIs to build user services, notification services, and authentication services.

Fintech Applications

Fintech platforms require fast response times and strong scalability. Minimal APIs are commonly used for transaction validation, balance checks, and payment status APIs. Their reduced latency helps ensure quick financial operations while maintaining security.

SaaS Platforms

SaaS applications use Minimal APIs to expose public APIs for integrations, dashboards, and analytics. The clean structure allows faster development and easier scaling as customer demand grows.

Common Mistakes Developers Make with Minimal APIs

Putting Too Much Logic in Endpoints

Endpoints should remain thin. Heavy business logic inside endpoints makes the code difficult to maintain. Always move logic to services.

Ignoring Validation

Relying only on basic checks can lead to data issues. Proper validation libraries should be used for production-ready APIs.

Overusing Middleware

Adding unnecessary middleware can reduce the performance benefits of Minimal APIs. Only include what is truly required.

Not Using Async Methods

Blocking calls reduce scalability. Always use async and await for database and external calls.

Treating Minimal APIs as Controllers

Trying to replicate controller patterns defeats the purpose of Minimal APIs. Keep the design simple and minimal.

Best Practices for High-Performance Minimal APIs

Keep endpoints small, prefer async APIs, minimize allocations, cache frequently used data, and monitor performance regularly. Performance is achieved through consistent design choices rather than a single optimization.

Summary

Minimal API architecture in .NET offers a modern, efficient way to build high-performance APIs with less code and better scalability. By using focused endpoints, dependency injection, async programming, efficient data access, caching, and careful middleware usage, developers can build fast and reliable APIs suitable for modern cloud and microservice environments. Choosing Minimal APIs helps teams deliver scalable solutions while keeping the codebase clean and maintainable.