I am going to create a separate site collection for my application in client's Office 365 tenant, however client has concern that their corporate data should not be crawled/indexed during Search. For this, I have proposed that we will create separate/custom Result sources specific to site collection, so that only my application data will be searched.
My question is - Can we create separate search index also per site collection in SharePoint Online, so that we can communicate to client that for their other site collections in the tenant, we will not use/touch their search index. OR do we have common search index in SharePoint Online.
NOTE - I am not referring here any kind of Hybrid environment, the question is specific to SharePoint Online (Office 365) only.