kay9 Now let’s say you wish to update the document with username janedoe to change the email address to janedoe74@example2.com.We build a completely new document which is identical to the original, except for the new email address.Imagine you want to increment the score property of the janedoe user.In order to achieve this with the replacement approach, you would have to first fetch the document, modify it with the incremented score, then write it back to the database.With that approach, you could easily lose other score changes if something else were to update the score in between you reading and writing it.These update modifiers include operators such as atomic increment/decrement, atomic list push/pop and so on.It is very helpful to be aware of which update modifiers are available and what they can do when designing your application.To illustrate usage of update modifiers, let’s return to our original example of changing only the email address of the document with username janedoe.We can use the $set update modifier in our update document to avoid having to query before updating.$set changes the value of an individual property or a group of properties to whatever you specify.# run the update query, using the $set update modifier.# we do not need to know the current contents of the document # with this approach, and so avoid an initial query and # potential race condition.# update the email address and the score at the same time # using $set in a single write.In other words, even if you believe your update document spec matches every single document in the collection, your update will