SharePoint - what type of permission required for user to execute application which is used Server object model API model

Hi

I investigated around what minimum permission required for user to execute Server object model API used application. I found that the unexpected result from different websites the user who is executing application required SharePoint database access. here are list of different database access required

1.  web application content database owner role

2. SharePoint config database owner role  

If this user doesn't have these access on these databases along with site-collection access which he is accessing then API throw - file not found exception.

So I am looking for any Microsoft  official document around this which shows minimum permission require to execute server model API. 

Is any one validate these permission ?

I am looking forward to hear some words from Microsoft person to clarify on this.

Thanks in advance