Firestore Cloud Function API Endpoint

I want anyone (unauthenticated users) to be able to call an API an return the tier of plan they are on depending on their FN, LN, DOB. I created an HTTP endpoint via a Cloud Function but receive a 403 error even after updating permissions.

import * as functions from "firebase-functions";
import * as admin from "firebase-admin";

admin.initializeApp();

export const checkEligibility = functions.https.onRequest(async (req, res) => {
  const firstName = req.body.firstName;
  const lastName = req.body.lastName;
  const dateOfBirth = new Date(req.body.dateOfBirth);

  console.log(firstName);

  const eligibleUsersRef = admin.firestore().collection("eligible_people");
  const querySnapshot = await eligibleUsersRef
    .where("firstName", "==", firstName)
    .where("lastName", "==", lastName)
    .where("dob", "==", admin.firestore.Timestamp.fromDate(dateOfBirth))
    .get();

  if (querySnapshot.empty) {
    // User is not eligible, return an error message
    res.status(403).send("User is not eligible");
  } else {
    // User is eligible, return the name of the tier
    const eligibleUser = querySnapshot.docs[0].data();
    res.json({tier: eligibleUser.tier});
  }
});

When I call this function from an app, I receive the following log:

Function execution took 4077 ms, finished with status code: 403

I've updated the permissions of this in the Google Cloud so that all users are invokers, similar to this: https://stackoverflow.com/questions/60237167/firebase-functions-https-403-forbidden. However, I'm still getting this 403 error--what am I doing wrong?

The result of the Timestamp.fromDate() method is different from the time Timestamp stored in the database. The consequence is that your querySnapshot is always empty.

Since you select on a date (and not a date/time) I advise to use a simple string formatted for example as YYYYMMDD.