login.js

const Redis = require("ioredis");
const redis = new Redis();

app.post("/login", async (req, res) => {
    const userId = req.body.userId;
    const timestamp = Date.now();
    const bitmapKey = `user_login:${userId}`;
    const offset = Math.floor(timestamp / (24 * 60 * 60 * 1000));

    await redis.setbit(bitmapKey, offset, 1);
    res.send("User login recorded!");
});