How to Create Cron Jobs in Firebase Functions Using Pub/Sub (Free Tier Compatible)

If you're building on Firebase, you might wonder how to implement scheduled (cron) jobs in a serverless setup. Firebase doesn’t have built-in cron support, but with Google Cloud Pub/Sub and Cloud Scheduler (with Firebase Functions), you can build reliable cron jobs — and best of all, you can do it within the free tier if you're careful. Why Use Cloud Scheduler with Firebase Functions? Fully serverless and scalable Low-maintenance once configured Compatible with the Firebase free tier for many use cases Step 1: Enable Required APIs In the Google Cloud Console linked to your Firebase project, enable: Cloud Scheduler API Cloud Pub/Sub API Step 2: Create the Pub/Sub Topic gcloud pubsub topics create my-scheduled-task Step 3: Deploy a Firebase Function that Listens to the Topic In your functions/index.js (or .ts): const functions = require('firebase-functions'); exports.scheduledFunction = functions.pubsub .topic('my-scheduled-task') .onPublish((message) => { console.log('Running scheduled job:', new Date().toISOString()); // Your logic here, e.g. data cleanup return Promise.resolve(); }); Step 4: Create a Cloud Scheduler Job gcloud scheduler jobs create pubsub run-my-scheduled-task \ --schedule="/15 * * *" \ --time-zone="UTC" \ --topic=my-scheduled-task \ --message-body="{}" This runs your function every 15 minutes. Modify the schedule string as needed. Pros and Cons ✅ Pros Integrates seamlessly with Firebase Uses managed services, very low maintenance Highly scalable and robust ⚠️ Cons Initial setup is more complex than other solutions May incur cost if usage exceeds free tier (e.g. high-frequency tasks) Limited visibility into execution logs unless using full GCP console

Apr 22, 2025 - 03:21

How to Create Cron Jobs in Firebase Functions Using Pub/Sub (Free Tier Compatible)

If you're building on Firebase, you might wonder how to implement scheduled (cron) jobs in a serverless setup. Firebase doesn’t have built-in cron support, but with Google Cloud Pub/Sub and Cloud Scheduler (with Firebase Functions), you can build reliable cron jobs — and best of all, you can do it within the free tier if you're careful.

Why Use Cloud Scheduler with Firebase Functions?

Fully serverless and scalable
Low-maintenance once configured
Compatible with the Firebase free tier for many use cases

Step 1: Enable Required APIs

In the Google Cloud Console linked to your Firebase project, enable:

Cloud Scheduler API
Cloud Pub/Sub API

Step 2: Create the Pub/Sub Topic

gcloud pubsub topics create my-scheduled-task

Step 3: Deploy a Firebase Function that Listens to the Topic

In your functions/index.js (or .ts):

const functions = require('firebase-functions');

exports.scheduledFunction = functions.pubsub
  .topic('my-scheduled-task')
  .onPublish((message) => {
    console.log('Running scheduled job:', new Date().toISOString());

    // Your logic here, e.g. data cleanup
    return Promise.resolve();
  });

Step 4: Create a Cloud Scheduler Job

gcloud scheduler jobs create pubsub run-my-scheduled-task \
  --schedule="*/15 * * * *" \
  --time-zone="UTC" \
  --topic=my-scheduled-task \
  --message-body="{}"

This runs your function every 15 minutes. Modify the schedule string as needed.

Pros and Cons

✅ Pros

Integrates seamlessly with Firebase
Uses managed services, very low maintenance
Highly scalable and robust

⚠️ Cons

Initial setup is more complex than other solutions
May incur cost if usage exceeds free tier (e.g. high-frequency tasks)
Limited visibility into execution logs unless using full GCP console