Hmmm… Part of the answer is going to depend upon how this is going to be used. Not just that you’re going to query on that field to identify a subset of items, but also determine whether there are other constraints or limitations involved.
For example, is there going to be a limit to the number of featured items? Who will have the authority to mark an item as featured or not? Is that authority different from the people who are adding or removing items? Does a featured item expire after some period of time? … or because of some external condition?
Does that “is_featured” flag itself show up in other places, to distinguish between featured and not-featured items in item lists?
You’ll want to identify the entirety of how this is going to be used and how it interacts with the rest of the site - then think about the queries or processing involved with handling each case - and consider the frequency of those operations.
Sometimes it’s a tradeoff - you may need to decide between an implementation that makes 90% of everything really easy and the other 10% very difficult, or a different implementation that makes everything somewhat average.
Bottom line is that “optimal” is rarely a yes/no answer, and it’s always extremely context sensitive - and it may even change over time as the application matures and evolves.