Saving Data on Android

Other features
Transac/ons
Realtime Database also allows you to write data to the database using a transaction. 
A database transaction is a unit of work that is independently executed and it must 
be atomic, consistent, isolated and durable. If the 
WhatsUp
 app had a feature to 
allow you to "like" a post you could use transactions to keep track how many 
likes
 a 
given post had. Since there is a use case where multiple users could "like" the post at 
the same time, the transaction would allow you to always have fresh and correct data 
about 
likes
.
Check the official documentation  
https://firebase.google.com/docs/database/
android/read-and-write#save_data_as_transactions
  to see how to work with 
transactions.