In Scala Collection documentation, there is some clue to this question:
Trait Seq has two subtraits LinearSeq, and IndexedSeq. These do not add any new operations, but each offers different performance characteristics: A linear sequence has efficient head and tail operations, whereas an indexed sequence has efficient apply, length, and (if mutable) update operations.
But this does not address me when to use IndexedSeq instead of Seq?
I need some real example of IndexedSeq or LinearSeq where these collections do better than Seq.