expired.js

const functions = require('firebase-functions')
const admin = require('firebase-admin')
admin.initializeApp(functions.config().firebase)

exports.hourly = functions.https.onRequest((req, res) => {
  const expiration = Date.now() + * 60 * 60 / 1000 // At least an hour old in seconds
  const ref = admin.database().ref("space")
  ref.orderByKey("timestamp").endAt(expiration).once("event", snap => {
    const vals = snap.val()
    Object.keys(vals).map(key => {
      ref.child(key).remove()
    })
  })  
})