Save money with this one Firestore free quota trick for CRON jobs

I’m sorry, but I just couldn’t resist that clickbaity title. 😛 Jokes aside, let’s say you have a monthly CRON job that empties out your users’ trash and does some other Firestore related cleanup. This is a great use of Firebase Cloud Functions, but it comes at a cost: you’re creating/updating/deleting documents all in one go.

Remember, Firestore free quota resets daily. So if you’re too small to max out your free quota everyday, but too big to stay on the Spark plan, you should consider running daily jobs instead.

As long as your Cloud Functions only query the data they’re going to process, then it’ll be far cheaper to run a job every day and take full advantage of that free quota. As an added bonus, you’ll be able to better predict your monthly bill because you’ll be spreading out Firestore usage over each day.

Running daily jobs

Running a daily CRON job is ridiculously easy to do: simply create aCloud Scheduler job set to run at 3am each morning(0 3 * * *) that publishes an empty data payload ({}) to a topic of your choice (daily-tick). It’ll look something like this:

This tick is completely free!

In your functions’ index file, subscribe to the daily-tick pubsub event and you’re good to go.

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Hopefully this will help you save a few bucks. Happy coding!