.NET guide — every framework

.NET rate limitingper API key, per plan.

One NuGet package for Minimal APIs, MVC controllers, and custom middleware. It checks each caller’s key, charges their credits, and applies their plan’s rate limit.

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  • Keys issued per customer
  • Credits that refill
  • Limits per plan, not per process

Official SDKs with drop-in middleware for the stack you already run

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API requests validated
100M+
Average key validation
<5ms
Average analytics ingest
<5ms
Check and log, end to end
<10ms

The usual .NET rate limiter counts requests. It doesn’t know your customers.

.NET 7 added first-class rate limiting — fixed, sliding, token-bucket, and concurrency limiters. They run in memory per instance and count requests; they don’t issue keys or keep balances.

With System.Threading.RateLimitingtoday
  • In-memory per instance
  • Partitioning by customer needs a key you already trust
  • No API keys: issuing, hashing, scoping, and revoking them is still yours to build
  • No credit balance: a request can’t cost 5 on one route and 1 on another, or refill each month
  • One limit for everyone — no per-plan limits for Free, Pro, and Enterprise customers
  • No per-customer usage log to answer “why was I blocked?” or bill against
With ReqKey in .NETone middleware
  • API keys issued per customer, prefixed, hashed, and revocable from the dashboard
  • A credit balance per customer — price each route, refill every hour, day, week, or month
  • Rate limits set per plan, shared by all of a customer’s keys, from 1 second to 24 hours
  • The same count on every worker, instance, and region — no Redis to run
  • Over the limit? A 429 with Retry-After, and no credits charged
  • Every request logged per customer — status, latency, endpoint — in under 5ms
HttpContext.GetReqKeyDecision() returns the verdict anywhere in the pipeline. See the code

.NET in three steps, one of them code.

ReqKey runs inside your API, not in front of it. Your server asks one question per request and gets an answer in under 5ms.

  1. 1

    Install the SDK

    dotnet add package ReqKey.AspNetCore

  2. 2

    Set your project key

    Copy it from the dashboard into REQKEY_PROJECT_KEY. It stays on your server.

  3. 3

    Add the middleware

    Every request is checked, charged, and logged before your handler runs.

Program.csdotnet add package ReqKey.AspNetCore
using ReqKey.AspNetCore;
 
var builder = WebApplication.CreateBuilder(args);
 
builder.Services.AddReqKey(options =>
{
    options.ProjectKey = builder.Configuration["REQKEY_PROJECT_KEY"];
    options.ApiId = "api_payments";
    options.KeyName = "X-Startup-Key";
    options.ExcludePaths = ["/health"];
});
 
var app = builder.Build();
app.UseRouting();
app.UseReqKey();
 
app.MapPost("/payments", (HttpContext context) => Results.Ok(new
{
    creditsRemaining = context.GetReqKeyDecision()?.CreditsRemaining,
}))
    .RequireReqKey(credits: 5, apiId: "api_images", resource: "/v1/images");
 
app.MapGet("/health", () => Results.Ok(new { ok = true })).SkipReqKey();
 
app.Run();
Also in .NET: ASP.NET Core, ASP.NET Core Web APIFull .NET reference

Every request gets one of these answers

  • 200Valid key, credits charged — your handler runs
  • 402Out of credits
  • 403Key disabled, or not allowed on this API
  • 429Over the rate limit — no credits charged

Where ReqKey sits

Your customer
Your APIReqKey, under 5ms
Your handler

Responses go straight back to your customer. ReqKey sees the key check and the log line, nothing else.

Credits

Charge each route what it costs you.

A lookup can cost 1 credit and a render 5, from the same balance. Excluded paths are never validated, charged, or recorded. In .NET:

Per-route credits · .NET
// Exact paths or trailing-* prefixes: never validated, charged, or recorded
options.ExcludePaths = ["/health", "/docs/*"];
 
// Or decide per request with a predicate
options.ShouldProtect = (context, _) =>
    ValueTask.FromResult(context.Request.Path.StartsWithSegments("/api"));
 
// Charge different endpoints differently
options.CreditCostResolver = (context, _) =>
    ValueTask.FromResult(context.Request.Method == HttpMethods.Post ? 5 : 1);
 
// Minimal APIs and MVC actions override cost per endpoint
app.MapPost("/images", HandleImage).RequireReqKey(credits: 5, apiId: "api_images");
// [ReqKey(Credits = 2, Resource = "/v1/orders")] on a controller action

Rate limits

Set limits on plans, not in code.

Your .NET code never hard-codes a number. Each plan carries its credits, refill, and rate limit; moving a customer to Pro changes all three with no deploy.

PlanCreditsRate limit
Free1,000 / month5 req / s
Pro50,000 / month50 req / s
Scale1,000,000 / month500 req / s
429Over the limit, a call is answered with Retry-After and costs nothing — no credits and no quota.

Example plans. You name them and pick the numbers.

Notes for .NET teams hit in production.

Endpoint-level pricing

RequireReqKey(credits: 5) on Minimal APIs, [ReqKey(Credits = 2)] on controllers.

Configuration binding

Options in code, or bound from appsettings.json.

Framework-neutral client

The ReqKey package works in workers, functions, and console apps.

.NET rate limiting: the questions teams ask.

Something else? Ask the team or read the docs.

  • Yes — reference the core ReqKey package and verify keys with the client.

  • For customer plan limits, yes. Concurrency limiters for your own protection can stay.

  • On their plan or on the customer (consumer) in ReqKey — a number of requests per window from 1 second to 24 hours, shared by all of that customer’s keys. Your .NET code never hard-codes a limit, so upgrading a customer is a dashboard change, not a deploy.

  • A check averages under 5ms. ReqKey runs inside your app as middleware, not as a gateway in front of it, so responses go straight back to your customer.

  • You choose: fail closed and answer 503, or fail open and let requests through. Invalid keys are denied either way, and a validation is never retried, so no one is charged twice.

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