If I want to check from a restApi call, if any items of a collection / query has changed since last visit, what is the best approach?
Can I somehow construct a timestamp that I can store (on a phone ) and compare it to 'last time a collection changed' (something was added/removed/modified)?
you can mdsum the concat of ids of object in the collection. you can use the sort approach if you don't care about ordering changes.
If you know the collection is small, you can directly store/compare the result of restapi call to get the collection members.
You can't really check for a collection (I think), but for single items you can check the modification date.
yes, but the 'list' will not be updated if an item has been deleted.
Yuris suggestions sounds like a good idea. I will try that when I get the time (it is just for a 'test project' integrating Flutter and Plone).