However, select queries is running fine. You notice that the server is running fine with less than 50 users. You use the SQL Profiler and found out that 3 columns of your table are heavily used in queries, ColA, ColB and ColC. ColA contains mostly the same data. ColC contains mostly unique data. You have an entity that has 10 attribute.
First attribute is the primary key.
The second attribute to the fourth attribute are foreign key to other table. The rest are attributes of the entity. The first one has the primary key and the 3 foreign key.