Using Firebase Firestore in offline only mode [closed]

Question

I'd like to use just a single method of persistence in my app, and am using Cloud Firestore for my premium/paying users.

Is it possible to also use Firestore in offline only mode for free users so that I don't incur costs?

Answer 1

Cloud Firestore is an online database that continues to work when you're offline for short or longer periods of time. But it's still primarily an online database, and should not be used as a fully offline database.

One reason for this is that Firestore keeps the local mutations in a separate queue until they've been committed to the server. When a query/read hits the local data, the Firestore client combines the cached reads that it got from the server, with the local mutations. As the queue of local mutations grows, this operation gets slower. As long as the client occasionally synchronizes the data to the server, this slow down won't be significant. But if you use Firestore as a fully offline database, it will become prohibitive over time.

For a good explanation of how the Firestore client works under the hood, have a look at these (long) code comments in the Firestore JavaScript SDK:

• the persistence class, which is responsible for storing the data on the local disk

• the local store class, which handles (a.o.) the reading from both the local cache and the local mutations.