RateLimit.Throttlr

A flexible and customizable rate limiting library for modern and legacy .NET APIs.

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Overview

RateLimit.Throttlr supports multiple rate limiting algorithms:

• Fixed Window
• Sliding Window
• Token Bucket

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Installation

Install via NuGet:

   dotnet add package RateLimit.Throttlr

Usage Example

Register in DI

using RateLimit.Throttlr.Core;
using RateLimit.Throttlr.Extensions;

var builder = WebApplication.CreateBuilder(args);

builder.Services.AddControllers();

// Add rate limiting services
builder.Services.AddRateLimiting(
    new RateLimitPolicy(
        name: "global",                        // unique policy name
        limit: 5,                               // max 5 requests
        window: TimeSpan.FromSeconds(10)       // per 10 seconds
    ),
    limiterType: RateLimiterType.SlidingWindow // Options: FixedWindow | SlidingWindow | TokenBucket
);

Configure Middleware

app.UseRouting();

app.UseRateLimiting(); // Apply rate limiting

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

app.Run();

Example Controller

namespace DemoAPI.Controllers
{
    [ApiController]
    [Route("[controller]")]
    public class WeatherForecastController : ControllerBase
    {
        [HttpGet("hello")]
        public IActionResult GetHello()
        {
            return Ok(new
            {
                message = "Hello, world!",
                timestamp = DateTime.UtcNow
            });
        }
    }
}

Behavior:

Each IP (or custom partition key) can only make 5 requests per 10 seconds. Exceeding the limit returns HTTP 429 Too Many Requests. Standard headers: X-RateLimit-Limit: total allowed requests X-RateLimit-Remaining: requests left in the current window X-RateLimit-Reset: Unix timestamp when window resets Retry-After: seconds to wait before next allowed request

Supported Algorithms

Limiter Type Description FixedWindow Counts requests per fixed window interval SlidingWindow Smooths counts using weighted previous window TokenBucket Allows bursts and steady refill rate