My Experience with MongoDB University Part 2: When Your Schema is changed

Just a small gotcha when You need to change your collection's schema in MongoDB. Basically, there are three general ways to go:

Just keep inserting documents with the new schema and leave old records intact. This might be an issue working with statically typed languages like C#, though.
Perform a bulk update on the existing documents.
An adaptive approach, when You update old documents to the new schema one by one at an appropriate event (such as getting read from or written to).

Craftsman at Work