You can send confirmation email to user before saving in database. Only user with valid email will be able to receive the email and click on the link to complete registration.

Create POST route

// routes/auth.js
router.post("/pre-register", auth.preRegister);

Create controller function

// controllers/auth.js
// create jwt with email and password then email as clickable link
// only when user click on that email link, registeration completes
export const preRegister = async (req, res) => {
  try {
    console.log(req.body);
    // to send email use AWS SES
    const emailSent = true;
    if (emailSent) {
      console.log("Check email to complete registration");
      return res.json({ ok: true });
    } else {
      console.log("Provide a valid email address");
      return res.json({ ok: false });
    }
  } catch (err) {
    console.log(err);
    res.json({ error: "Something went wrong. Try again." });
  }
};

No try making POST request using Postman and check your server console.