What is the difference between $isolated and findAndModify in mongodb?

Question

The $isolated and findAndModify in mongodb both prevent other processes change the document. I am confused about the different of this two method, what is the difference between them?

Answer 1

findAndModify does not prevent other processes change the document.

Let's say that processes A and B both try to update a document at the same time.

With $isolated:

1. A finds the document
2. B wants to find the document but it's prevented
3. A updates the document
4. B finds the document
5. B updates the document
6. document value is B

With findAnyModify:

1. A finds the document
2. B finds the document
3. B updates the document
4. A updates the document
5. document value is A

Further reading: What's the difference between findAndModify and update in MongoDB?