Erik Darling finds an eager spool even when there is a good index to use:
But he did write about Eager Index Spools recently, and the post ended with the following statement:
Eager index spools are often a sign that a useful permanent index is missing from the database schema.
I’d like to show you a case where you may see an Eager Index Spool even when you have the index being spooled.
Click through for Erik’s demonstration.