userCache.js

/**
 * Fetches the session user from cache if it exists, or sets it if it does not
 */
const getOrSetUserFromCache = async headers => {
  const User = require('../models/User');
  const userUid = headers['x-userid'];

  try {
    const firebaseUserUid = await User.getUserIdFromToken(headers.authorization);
    if (!userUid || firebaseUserUid !== userUid) {
      userCache.del(`firebase-${userUid}`);
      return User.getCurrentUserByToken(headers.authorization);
    }

    const userFromCache = userCache.get(`firebase-${userUid}`);
    if (userFromCache) {
      return userFromCache;
    }

    const user = await User.getCurrentUserByToken(headers.authorization);
    userCache.set(`firebase-${userUid}`, user, FIVE_MINUTES); // Set TTL
    return user;

  } catch (e) {
    throw new Error('Invalid user token');
  }
};