Is there a need to index the short string code for a faster query?

We have a large number of tables for setup forms. In each form, there is a need to fill in the Code and the Description. The Code consists of a varchar(10) datatype. Now, the thing is, every time a user creates new data or updates the data, there is a need to check whether the Code conflicts with the others or not. In LINQ, this code checking is inevitable: string ExistingCode = "ITEM01"; int ExistingKey = 1; var recordWithConflictedCode = (from a in db.MyTable where a.Code == ExistingCode && a.Key != ExistingKey).ToList(); if(recordWithConflictedCode.Count >= 1) return BadRequest("Duplicated Code found"); Now, since this involves a string comparison on every process, I think it makes sense to index the column Code to make the query faster. Is this a common practice for you guys?