The policy for deciding which member to delete is as follows:

• If any members are in a FAILED state, those will be removed (if this is more than the number you want to scale down by, the difference will be made up by new members being created).
• The members with the oldest created_time in the database are removed first.
• In the event of a tie (creation times have only 1s of resolution), the members with lexicographically smaller names are removed first (i.e. member 'aa' will be removed before member 'ab').