I am still new in the React Native world, and generally in the mobile/native world as well, and I am finding the documentation a bit lacking when it comes to data persistence.
What are my options for storing data in React Native and the implications of each type? For instance, I see that there is local storage and async storage, but then I also see things like Realm, and I'm confused how all of this would work with an outside database.
I specifically want to know:
Here's what I've learned as I determine the best way to move forward with a couple of my current app projects.
Async Storage ("built-in" to React Native)
I use AsyncStorage for an in-production app. Storage stays local to the device, is unencrypted (as mentioned in another answer), goes away if you delete the app, but should be saved as part of your device's backups and persists during upgrades (both native upgrades ala TestFlight and code upgrades via CodePush).
Conclusion: Local storage; you provide your own sync/backup solution.
Other projects I have worked on have used sqlite3 for app storage. This gives you an SQL-like experience, with compressible databases that can also be transmitted to and from the device. I have not had any experience with syncing them to a back end, but I imagine various libraries exist. There are RN libraries for connecting to SQLite.
Conclusion: Local storage; you supply the sync and backup.
Conclusion: Network first, no RN caching. Scales well for network-connected devices. Low cost for low utilization. Combines nicely with other Google cloud offerings.
Also a real time object store with automagic network synchronization. They tout themselves as "device first" and the demo video shows how the devices handle sporadic or lossy network connectivity.
They offer a free version of the object store that you host on your own servers or in a cloud solution like AWS or Azure. You can also create in-memory stores that do not persist with the device, device-only stores that do not sync up with the server, read-only server stores, and the full read-write option for synchronization across one or more devices. They have professional and enterprise options that cost more up front per month than Firebase.
Unlike Firebase, all Realm capabilities are supported in React Native and Xamarin, just as they are in Swift/ObjC/Java (native) apps.
Conclusion: Device first, optional synchronization with free and paid plans. All features supported in React Native. Horizontal scaling more expensive than Firebase.
I honestly haven't done a lot of playing with this one, but will be doing so in the near future.
If you have a native app that uses CloudKit, you can use CloudKit JS to connect to your app's containers from a web app (or, in our case, React Native). In this scenario, you would probably have a native iOS app and a React Native Android app.
Like Realm, this stores data locally and syncs it to iCloud when possible. There are public stores for your app and private stores for each customer. Customers can even chose to share some of their stores or objects with other users.
Conclusion: Great for Apple-targeted apps.
Big name, lots of big companies behind it. There's a Community Edition and Enterprise Edition with the standard support costs.
They've got a tutorial on their site for hooking things up to React Native. I also haven't spent much time on this one, but it looks to be a viable alternative to Realm in terms of functionality.
[Edit: Found an older link that talks about Couchbase and CouchDB, and CouchDB may be yet another option to consider. The two are historically related but presently completely different products. See this comparison.]
Conclusion: Looks to have similar capabilities as Realm. Can be device-only or synced. I need to try it out.
I'm using this server side for a piece of the app that uses AsyncStorage locally. I like that everything is stored as JSON objects, making transmission to the client devices very straightforward. In my use case, it's used as a cache between an upstream provider of TV guide data and my client devices.
I have not tried any client to server synchronization features, nor have I used it embedded. React Native code for MongoDB does exist.
Conclusion: Local only NoSQL solution, no obvious sync option like Realm or Firebase.
My next few React Native apps will probably use Realm or Couchbase; I anticipate those that could leverage Firebase the best will probably be written in Swift.