SharePoint 5000 item limit threshold in sharepoint 2016

I know the issue is quite old and solved too many times , but for my case the solution should be faster and sophisticate as much as I can.

The case is, my sites are migrated from SharePoint 2013 to SharePoint 2016 with WSS_content migrations. The number of items in libraries are growing with un-controlled way, more than 20,000 and 30,000 item in one library.

As we know in SharePoint we have the problem of 5000 item limit threshold, but this is the case for SharePoint 2013, with SharePoint 2016 it should be resolved to 10,000, but not in my case.

So I have a simple web part to get the last modified/added items from libraries using CAML query, this web part on the extended libraries doesn’t give me the correct results.

Here are some solutions Sharepoint Online Document Library 5000 view threshold, index columns and the recommended Microsoft way.

So, what is the best solution?

  1. Index the modified and created column of all the libraries.
  2. Update the CAML query?
  3. Replace the old web part by a new the content search web part(How it works for multi libraries any suggestion)?

I cant add managed meta data or update the content type, because the sites are migrated and I should not modify the structure.