This seems easier to answer than the previous version ^^
If I remember correctly, the ComboBox is entirely initialized when send from the server. So it will not do any lazy loading when creating the page and will take a long time with any container.
You could do the same kind of feature as the combobox with a table and a filter as in
this sample . This would give you lazy loading which would render faster but keep in mind that filtering through that huge amount of data will still take a fair amount of time…