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, they 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.