CosmosDB Mongo - What's the better way to check if an array is empty ?

Question

Hey I want to check if some of my arrays on a document are empty. Right now I'm doing a simple

{"myArray": []}

(eq operation), because I know that using the $size operator would prevent MongoDB to use any indexes (it would be like this :

{"myArray": {$size: 0}}

But since MongoDB and CosmosDB have some discrepancies (especially the indexes doesn't work the same), I wondered if this was really the case when using Cosmos ? I didn't find anything related in the documentation. Thanks for your help.