I'm developing an app for distributors which gives them a list of stores and they note in the app how many products did they sell to any store. This is the main function of my app. There are two choices: firebase realtime database or Cloud Firestore. I need only speed and less pricing. Please tell me how their pricing does work and also which one is faster? Explain shortly please.
You should check the official docs. And get a proper idea between these two. There are things you need to consider before choosing either of them. According to your goal, both will help you in different ways.
Realtime and offline support, Querying, Writes and transactions, Reliability and performance, Scalability, Security, Pricing, Data Model. These are the things you need to consider while choosing either of these.
I would like to suggest this link though.
You should think more carefully the future work load your environment will have. That will give you better ground to evaluate the pricing. In general, I would prefer to use Firestore because it is the new one and it is superior when it comes to scaling the service. It will scale automatically as your user base grows and will not need any sharding in high volumes.