Develop Reference

Is it possible to sync with different server database in a single app

I want to make an Android App, where I want to sync with different server database to store my data. Like for example Firebase database, AWS Database etc and sync accross them same time. Also with different firebase database account at the same time vise versa with AWS too
Any clue anyone, is it possible? If it is will there be latency during synchronisation.

How Not to Pull Data From Firebase at Every Startup of the App #AskFirebase

I am building an app for a gym which shows gym members info in a recyclerview at the app startup , the problem is at every fresh launch of the app the data is pulled from the firebase database and appears suddenly after 4-5 seconds in the recyclerview after the app starts, and i think this time will increase as the data grows.
If the data is same why pull it every time.
But i want to go one step further
what i want is when the user logs in for the first time all the data liked to that account should get pulled off and stored locally , i don't want to pull the data ever again even if the user is connected to internet, the changes user make should be made to realtime database as well as locally regardless how much data is created , so that i never need to pull data again once the user is logged in but just push the data every time it changes or grows or gets deleted, operations will happen to both local storage as well as at realtime database, so the user will always have local access to data he created.
And if he logs in again same thing happen again.
Is there a way to do it with firebase without implementing local sqlite database together with firebase realtime database.

This answer is for a use case where data is stored locally as well as on a remote server - similar to what's in the question. It may not specifically answer the question but may lead to a solution.
In the question, it appears there's local data and remotely stored data which are essentially the same - the OP is using sql to store locally and Firebase to store remotely. This is being done to 'speed up' the loading process and lower the amount of reads.
My suggestion is to use Firebase only. It's very fast and if coded correctly, the loading time should never be 4-5 seconds before the UI is available to the user (barring a bad internet connection if not using persistence).
Additionally, Firebase offers locally persisted data in two ways; cached data and persisted data (which are similar but read on)
Cached: Firebase apps automatically handle temporary network interruptions.
Cached data is available while offline and Firebase resends any writes
when network connectivity is restored.
and
Persisted: By enabling persistence, any data that the Firebase Realtime Database
client would sync while online persists to disk and is available
offline, even when the user or operating system restarts the app. This
means your app works as it would online by using the local data stored
in the cache. Listener callbacks will continue to fire for local
updates.
There's a lot more to it so please see iOS Offline Persistence and Enabling Offline Capabilities on Android

Your questions suggests that the Firebase SDKs provides this sort of functionality. It does not. You will have to implement something yourself.

The best way to tackle this in an easy and the most efficient way is to use the Room Persistence provided by AndroidX Architecture.
It is technically an ORM over SQLite. Please find the details here:
AndroidX Room Persistence

Sync firebase database with sqlite database in Android

I'm using sqlite to store data in my app, i would like to sync my database with firebase so that i can do modify data from firebase and insert it into my database without updating the app. Any suggestions how can i do that.

You don't need to sync Firebase with your local database. Firebase provides you SDK to perform read/write operations in your database. You might only need to update your application if there is a schema change. That too can be achieved without keeping the computation logic in the Cloud and instead call Cloud Functions for cases where you know there are going to be a lot of schema changes.
Firebase provides you really well documented APIs and code samples. You can refer the following links for more information:
Firebase Docs -- SDKs here
Cloud Functions -- For cloud computation
Realtime Database -- Database for realtime transfer, can be costly for high usage. Generally used for PoC or low traffic projects
Firestore -- Upgraded version of Realtime DB. Generally used for high traffic.

Switching from SQLite to Firebase?

So for my Android App which stores data of workouts I have been using a SQLite Database so far. Now I want to implement these features:
Offer workouts in real time (with Firebase Database)
Being able to access your data on other devices and maybe from an web app
later
I figured, that for this purpose Firebase would be a great fit. But switching from SQLite to Firebase would bring a few down sights in my opinion:
Every user would need to sign up. I think for some users this is a reason to
not use my app. There is no way to avoid having to sign up when using
Firebase to store the data for user, right?
I´m not sure how good the offline options of Firebase Database is. How long
will the data be accessible without a connection? Is the capacity and
performance comparable to a SQLite Database?
I thought an alternative way could be to use Firebase just for offering the workouts but keep the data about a workout (repetitions, weight, ...) in a SQLite Database. Then I could upload the Database File with Firebase and another Device could download and continue it. Could that be an option?
Any thoughts and advice are appreciated!

Every user would need to sign up. I think for some users this is a
reason to not use my app. There is no way to avoid having to sign up
when using Firebase to store the data for user, right?
Right. (Technically it is possible, however you will need to enable read / write operations to non registered uses which is a no-no and not recommended at all.)
I´m not sure how good the offline options of Firebase Database is. How
long will the data be accessible without a connection? Is the capacity
and performance comparable to a SQLite Database?
From the firebase database docs: Firebase apps automatically handle temporary network interruptions. Cached data is available while offline and Firebase resends any writes when network connectivity is restored..
So yes, you can continue writing to it even when offline and read the already cached data, but this does not solve your concern that users will have to register to use the app.
Possible solution
Use both SQLite and Firebase database:
For a registered user, always write in both SQLite and Firebase to keep them in sync (write in Firebase first and then SQLite). Another option is to write in SQLite and sync to Firebase every X minutes. Read data from Firebase when online and from SQLite when offline.
When the user is offline, you will to write data to SQLite. You will need to mark those records as non-synced so that next time it is connected you will write them to firebase.
Also, when reconnected, you'll need to somehow merge firebase data (that might have changed) and local SQLite data. The algorithm for this depends on your app.
For non-registered users, use SQLite only.
The downside to all this is that the complexity of your application increases a lot. It's up to you to decide whether it's worth it or not. :)

Firebase instead of SQLite

I have been using SQLite as my storage solution for my android applications. I want to be able add synchronization functionality to one of my apps, Firebase looks like a good solution but the problem is that I need to know if I am to use Firebase to sync data with the SQLite database or Firebase can work and totally replace SQLite. I know Firebase has offline persistence but while offline can it hold as much data as SQLite and are the queries as powerful?

Clearly this depends on the business rules for which the options are considered. So there will not be the "right" answer to this.
At least one of our team members was thinking along these lines. Here is our solution:
Do all transactional data locally on the SQLite as we do not need transactions to be across devices.
Sync the rest using Firebase.
(1) makes sure that we don't misuse Firebase's non-persistent offline availability of its client.
The docs
Even with persistence enabled, transactions are not persisted across app restarts. So you cannot rely on transactions done offline being committed to your Firebase Realtime Database. To provide the best user experience, your app should show that a transaction has not been saved into your Firebase Realtime Database yet, or make sure your app remembers them manually and executes them again after an app restart.
(2) make sure that we use Firebase's persistent offline nature to synch non-transactional data across devices once connection is (re)established.
The docs, The Firebase Realtime Database client automatically keeps a queue of all write operations that are performed while your app is offline. When persistence is enabled, this queue is also persisted to disk so all of your writes are available when the user or operating system restarts the app. When the app regains connectivity, all of the operations are sent to the Firebase Realtime Database server.
This way we achieve a state acceptable within our use.
"can it hold as much data as SQLite and are the queries as powerful?" no and no if powerful is translated as "transaction across devices", by definition of Firebase being a remote database.