Index not used on Non Archived Collections when connected to Cluster AND Online Archive

Hi, I’m aware that when using Online Archive,
We have to use partitions in order to achieve a satisfactory performance.
However, it wasn’t clear that, when connected through the connection string that connects to both cluster and online archive, indexes wouldn’t be used for any collection.
Is that the expected behaviour or that’s something wrong with my application?
Thanks in advance for any help.