Using Clerk with Upstash for Middleware rate limiting and API Protection

middleware.ts

import { getAuth, withClerkMiddleware } from "@clerk/nextjs/server";
import { NextResponse, NextFetchEvent } from "next/server";
import type { NextRequest } from "next/server";
import { Ratelimit } from "@upstash/ratelimit";
import { Redis } from "@upstash/redis";

// Add public paths for Clerk to handle.
const publicPaths = ["/", "/sign-in*", "/sign-up*", "/api/blocked"];

// set your rate limit.
const ratelimit = new Ratelimit({
  redis: Redis.fromEnv(),
  limiter: Ratelimit.cachedFixedWindow(1, "10s"),
  ephemeralCache: new Map(),
  analytics: true,
});

// This checks if the pathname you are is public
const isPublic = (path: string) => {
  return publicPaths.find((x) =>
    path.match(new RegExp(`^${x}$`.replace("*$", "($|/|\\.)")))
  );
};
// this checks if you are hitting an API
const isAPI = (path: string) => {
  return path.match(new RegExp(`^\/api\/`))
}

export default withClerkMiddleware(async (request: NextRequest, event: NextFetchEvent) => {
  //Rate limit apis.
  if (isAPI(request.nextUrl.pathname) && request.nextUrl.pathname !== '/api/blocked') {
    const ip = request.ip;
    const { success, pending, limit, reset, remaining } = await ratelimit.limit(`ratelimit_middleware_${ip}`);
    event.waitUntil(pending);

    const res = success ? NextResponse.next() : NextResponse.redirect(new URL("/api/blocked", request.url));

    res.headers.set("X-RateLimit-Limit", limit.toString());
    res.headers.set("X-RateLimit-Remaining", remaining.toString());
    res.headers.set("X-RateLimit-Reset", reset.toString());
    return res;
  }
  // do nothing
  if (isPublic(request.nextUrl.pathname)) {
    return NextResponse.next();
  }
  // if the user is not signed in redirect them to the sign in page.
  const { userId } = getAuth(request);

  if (!userId) {
    // redirect the users to /pages/sign-in/[[...index]].ts

    const signInUrl = new URL("/sign-in", request.url);
    signInUrl.searchParams.set("redirect_url", request.url);
    return NextResponse.redirect(signInUrl);
  }
  return NextResponse.next();
});

// Stop Middleware running on static files
export const config = {
  matcher: [
    /*
     * Match all request paths except for the ones starting with:
     * - _next
     * - static (static files)
     * - favicon.ico (favicon file)
     */
    "/(.*?trpc.*?|(?!static|.*\\..*|_next|favicon.ico).*)",
    "/"
  ],
};