Concurrency on DocumentDB

Question

This is a newby question on DocumentDB. We want to use DocumentDB for our application. We have multiple users changing data that is stored in a DocumentDB. How can we asure that one user does not overwrite the changes of another user?

Answer 1

DocumentDB has optimistic concurrency and has an ETag on each document. If the ETag has changed when doing a write, the write fails (if the ETag changed, that means someone else modified the document). In this condition, you'd need to re-read and re-modify the document in question.

See the faq here for more info.