Throttling Limit not working in Custom Code.

Hi All 

I am trying to query 20 items from a list of 60000 items(10000 are folders & each folder has 6 items) in a visual webpart and facing below issue. 

Throttled:Big list slow query. List item query elapsed time: 0 milliseconds, Additional data (if available): Query HRESULT: 80070024 List internal name, flags, and URL: {1C571005-7FFB-4630-938D-6FCB4BA74A69}, flags=0x0000000020c01100, URL="Current User: 2 Query XML: "<Query><Where><Eq><FieldRef Name="FSObjType"/><Value Type="Integer">1</Value></Eq></Where></Query>" SQL Query: "N/A"            8d3ce5a1-01c2-4611-8153-e17e8f68ea74
The attempted operation is prohibited because it exceeds the list view threshold enforced by the administrator.                8d3ce5a1-01c2-4611-8153-e17e8f68ea74
04/10/2014 17:09:43.74 w3wp.exe (0x0FB8)                       0x1034  SharePoint Foundation                 Health                                   46ri                High       big list slow query, list:{1C571005-7FFB-4630-938D-6FCB4BA74A69}  viewname: viewxml: <View><Query><Where><Eq><FieldRef Name='FSObjType' /><Value Type='Integer'>1</Value></Eq></Where></Query><ViewFields><FieldRef Name='DOCNo' /><FieldRef Name='Title' /></ViewFields><RowLimit Paged="TRUE">20</RowLimit></View>            8d3ce5a1-01c2-4611-8153-e17e8f68ea74

If we change throttling limit it is working fine, but we are not allowed to do that in production

<View><Query><Where><Eq><FieldRef Name='FSObjType' /><Value Type='Integer'>1</Value></Eq></Where></Query><ViewFields><FieldRef Name='DOCNo' /><FieldRef Name='Title' /></ViewFields><RowLimit Paged="TRUE">20</RowLimit></View

In the Query I am trying to fetch only folders in the list with Rowlimit of 20. but  it is not working.

But if I navigate to same List Allitems View, ListViewwebpart is able to load 30 items/page with out any errors,with default throttling limits. No sure how Microsoft is handling it.

Initially I felt we implemented paging wrongly . So we have changed our paging logic to the way it is implemented in SharePoint default using SPListItemCollectionPosition object & indexed all the fields in the List.

http://ajamaeen.blogspot.com/2013/02/paging-with-splistitemcollectionposition.html 

ragava_28