In my current application, I store a value in Firestore for each user something along the lines of this:
User1Doc - hasUsedFeatureToday = true
User2Doc - hasUsedFeatureToday = false
...

At the end of the day, I run a scheduled function that resets all of these to false. This was fine while my application was relatively small, but does not scale very effectively as I'm sure you can imagine.

Each user can only use this aspect of my app once per day, so the only time this field is read is when they try to use it.

I would like to change this system to store a timestamp in the user's document when they use the feature and then check if this timestamp is the same day (Europe/London time) if someone tries to use it again.

Does Firebase offer a way to get a "timezoned" timestamp like this and store/check it with the Firestore?

CodePudding user response：

You can just store a timestamp (UTC). Whenever users logs in to your app, just check the timestamp and update the same. You can always use libraries like Luxon to get local time from the UTC time.

If you want to allow the user to update this timestamp only once, you can use security rules to restrict the same. However, user may try to prevent the timestamp from being updated at first place.

You can instead use Cloud Function to serve the data only when the user requests it. This will be better than updating documents of all users even if they won't be using the feature every day.