Separate Index or Composite Indice ?

10gR2 If you have : 2 columns on a hi-traffic transactional table - one ("some_id") high cardinality - and one ("yes_no") low cardinality You use both columns in SQL - "some_id" is used in JOIN and "yes_no" as a predicate Would you create normal index on BOTH , just "some_id" or a composite indice