Next.js の API で ip アドレスで rate limit をかける方法

yarn add lru-cache request-ip
yarn add -D @types/lru-cache @types/request-ip

import LRU from "lru-cache";

import type { NextApiResponse } from "next";

type CheckLimitFunc = () => {
  check: (res: NextApiResponse, limit: number, ipAddress: string) => Promise<void>;
};
export const LimitChecker: CheckLimitFunc = () => {
  const tokenCache = new LRU<string, number>({
    max: 500, // Max 500 users per interval
    maxAge: 1000 * 60 * 5, // 5分,
  });

  return {
    check: (res, limit, token): Promise<void> =>
      new Promise((resolve, reject) => {
        const tokenCount = tokenCache.get(token) || 0;

        const currentUsage = tokenCount + 1;
        tokenCache.set(token, currentUsage);

        const isRateLimited = currentUsage > limit;
        res.setHeader("X-RateLimit-Limit", limit);
        res.setHeader("X-RateLimit-Remaining", isRateLimited ? 0 : limit - currentUsage);

        return isRateLimited ? reject("Too Many Requests") : resolve();
      }),
  };
};

// pageExtensions の設定をしているので .page.ts になっています
import requestIp from "request-ip";

import type { NextApiRequest, NextApiResponse } from "next";

import { LimitChecker } from "@/lib/limitChecker";

const limitChecker = LimitChecker();

type Data = {
  text: string;
  clientIp: string;
};
export default async function handler(req: NextApiRequest, res: NextApiResponse<Data>): Promise<void> {
  const clientIp = requestIp.getClientIp(req) || "IP_NOT_FOUND";

  try {
    await limitChecker.check(res, 3, clientIp);
  } catch (error) {
    console.error(error);

    res.status(429).json({
      text: `Rate Limited`,
      clientIp: clientIp,
    });
    return;
  }

  res.status(200).json({
    text: `テキスト`,
    clientIp: clientIp,
  });
}