How to get document one time and using it every where - node.js

Question

I using firebase admin and use nodejs get data by phone number from firebase. When i get success , i want get only document one time and use it every time. It possible ?
Picture :
First i get document by phone look like.
Example:
const phone = await admin.firestore().collection('users').where('phone_number', '==', phone).get()
After that , i want using document phone every time in my code look like :
await handleLogic(phone)
Then
async function handleLogic(phone) {
//inside here i need call await admin.firestore().collection('users').where('phone_number', '==', somePhone).get() or re use phone in parameter ?
phone.ref.collection("subcollection").get()
.then(() => {
let data = {
created_at: timeNowFirebase(),
};
phone.ref.collection(subcollection).doc(someId)
.set(data);
}
I have question : Inside function handleLogic(phone), i need re call admin.firestore().collection('users').where('phone_number', '==', phone).get() or only use parameter phone and used phone.ref.collection(subcollection).doc(someId).set(data); . It will set subcollection into document my phone correct ?

Answer 1

Yes you can store the document ID (or even the DocumentReference as you are currently) in memory/cache instead of querying the document with phone number every time. The doc ID never changes and this seems to be a good way to prevent additional requests to the database.
// storing in memory for example
const phoneToUserId = {};
async function handleLogic(phone) {
if (!phoneToUserId[phone]) {
// run a query to get userID from phone number
const user = await admin.firestore().collection('users').where('phone_number', '==', somePhone).get()
phoneToUserId[phone] = user.docs[0].id
}
// get a reference to sub-collection
const subCol = admin.firestore().collection(`users/${phoneToUserId[phone]}/subcollection`)
// query data
}
However do note that you'll have to update that object whenever user updates their phone number or delete their document.