Hi @DeviB_  You can use OOTB Metadata Import tool to add metadata to all assets, this has batch limit of 100 which means from csv it will pick assets in batch of 100 until all asset is not updated. I have used this to update approx 70K assets and found no issue.You can go through below link for prep...

@aaront75403218Did you find any solution to this? I have similar requirement : Creation of Mixed Media Sets via Batch Set Presets in aem cloud.

Still in AEM as cloud service we don't have option to create Batch Set Preset for mixed media, please share if you have figure it out how to do this? @paul_macyg74957  

@Nishant-Singh  It's not working, still it keeps processing 

@Nishant-Singh We are able to create mixed media set programmatically and node hierarchy is also same as out of box functionality  but rendition folder is by default empty.Do you have any idea how can we generate renditions for mixed media set which will create thumbnail.Programmatically created nod...