Firebase Realtime Database vs Firestore.
FireStore is Google’s new database it is a NoSQL database and it’s amazing. It is fast, more intuitive and you can make queries with the database. Firestore can fetch queries. But Firebase was an amazing real-time database but there were some limitations with that database you can either sort or can filter in that database. But all these kinds of drawbacks which were in firebase's real-time database now have been overcome in Firestore.
In firebase real-time database has some kind of offline support for Android as well as iOS. BUT in FireStore has the complete support for offline access and offline data management capabilities for Android and iOS as well as for the web which means you can design your progressive web apps quite easily using the Firestore.
In firebase's real-time database you have to perform all write operations in just one single query or single thread in a kind of situation.
BUT in Firestore you can make them as a batch process so that you can collect all your data which you need to write in a database and just can process them as a batch operation, this itself is a long lifesaver.
Also in the firebase real-time database wherever you do a transaction you need to write a callback function if you remember that, BUT in Firestore you don’t need to write a callback, it will automatically be repeated until the transaction is complete.
One major big thing here now scalability was a little bit issue but not much in such if you are big organization one thing has starved you of using the firebase in the past was its ability to scale the data like hundred thousand concurrent connections and a huge speed to write the data is good in Firebase database, but your data grows your database is not such much scalable, you have to share your data in multiple databases (distributed) so that you can do scalability thing.
BUT in Firestore they are promising that this is not going to be a situation no matter how big your database is going to be it will completely be scalable in a Firestore, so it will be a big solution for big-scale industries.
In conclusion, I will recommend you to use the Firestore database rather than the firebase realtime database. In price issues, the Firestore database they are charging based on write and read operations that you’re performing on the databases.