如何减少电子邮件发送时间（使用nodemailer和firebase）？

当新节点添加到 Firebase 实时数据库中的特定路径时，我们编写了向用户及其联系人发送电子邮件的代码。

发送电子邮件的平均时间为 4 分钟。我们认为问题是由于等待一些必要的承诺。我们希望缩短运行时间。你有什么建议吗？提前致谢！

这是我们的代码：

const functiOns= require("firebase-functions");
const nodemailer = require('nodemailer');
require('dotenv').config()
//for fire store
const admin = require('firebase-admin');
admin.initializeApp();
const db = admin.firestore();
const { SENDER_EMAIL, SENDER_PASSWORD } = process.env;
exports.sendEmails = functions.database.ref("/devices/{device_ID}/history/{alert_ID}")
.onWrite(
(snapshot, context) => {
sendMail(snapshot, context);
return true;
}
);
async function sendMail(snapshot, context){
const { before, after } = snapshot;
// new alert created
if (before.val() == null) {
console.log('DEBUG:: NEW ALERT');
// get owners uID from device ID
const deviceRef = db.collection('deviceToUid').doc(context.params.device_ID);
const uidDoc = await deviceRef.get();
if(!uidDoc.exists){
functions.logger.info("No such document!");
return;
}
// get users email from uID
const userRef = db.collection('users').doc(uidDoc.data()[context.params.device_ID]).collection('user-info');
// get users contact
const cOntactRef= db.collection('users').doc(uidDoc.data()[context.params.device_ID]).collection('contacts');
const [userInfo, contactList] = await Promise.all([userRef.get(), contactRef.get()]);
if(userInfo.empty){
functions.logger.info("No such collection!");
return;
}
const email = userInfo.docs[0].id; // owners email
let cOntacts= []; // initialize contact list
contactList.forEach(
(doc) => {
if(doc.data().confirmed){
contacts.push(doc.id);
}
}
)
const mailTransport = nodemailer.createTransport({
service: 'gmail',
auth: {
user: SENDER_EMAIL,
pass: SENDER_PASSWORD,
},
});
const mailOptiOns= {
from: 'ALERT ',
to: email,
bcc: contacts,
subject: `...Motion detected`,
html: `

New Alert...

我还建议学习一些关于列表推导式的知识，如下所示：

let cOntacts= []; // initialize contact list
contactList.forEach(
(doc) => {
if(doc.data().confirmed){
contacts.push(doc.id);
}
}
)


可以简化为更简洁：

let cOntacts= contactList.docs
.filter((doc) => doc.data().confirmed)
.map((doc) => doc.id);