Using the $expand parameter with calls to the Microsoft Graph is very handy. In one API call you can retrieve both the object itself and additional properties.
Two examples are fetching a user and the direct reports, or a group and it’s members.
https://graph.microsoft.com/beta/users/061353c3-af75-4767-9b19-a5bceed85f53?$expand=directReports
https://graph.microsoft.com/v1.0/groups/79958190-024b-4c62-ab55-65dc9a066cac?$expand=members
The caution is that when you expand a property which has a collection of values, you will only get the first 20 items returned. This means that if you work in an organization with more than 20 people in it, you should not use $expand if you need all the values, but resort to two calls instead, one for the item, and one for the property you want to expand.
Summary
While using expand is very handy, it’s almost always better to break it into two API calls to avoid having issues if you can expect more than 20 items.
