- The sort key is limited to a single numeric or DATE column.
- The sort key column cannot exceed four bytes in length.
- If defined over multiple columns and with an ORDER BY clause, value-ordered NUSIs count as two consecutive indexes against the total of 32 non-primary indexes you can define on a base or join index table. This includes the system-defined secondary indexes used to implement PRIMARY KEY and UNIQUE constraints.
One index represents the column list and the other index represents the ordering column.