Cloud Firestore document read cost for subcollections?

Question

How to calculate firestore cost? I know that it count every operation, but if I read one document that contain sub collection how it count?

For example, If I read "A Document" that has 1 "Sub-Collection B" and "Sub-Collection B" have 5 document. Then how much it could if I only read "A Document", it will count 1 or 5 operation?

Answer 1

The location of a document has no bearing on the billing for its reads. It could be in a collection, or a subcollection, or a subcollection of a subcollection - it just doesn't matter. One document read always costs the same.