Are you using MySQL in your example? > id is an incremental value, I choose 11 as a length for this primary key but this value is defined by the number

Are you using MySQL in your example? > id is an incremental value, I choose 11 as a length for this primary key but this value is defined by the number of pages you’ll need to index This is a bit confusing. You'd generally be better off with INT UNSIGNED as it doubles the range for auto-increment columns. Also the visited field would be better to be represented by a timestamp, choosing the right datatype does matter in large tables.