Since the original SORT has a
STORE option it is technically flagged as a writing command in the Redis command table. For this reason read-only replicas in a Redis Cluster will redirect it to the master instance even if the connection is in read-only mode (see the READONLY command of Redis Cluster).
Since Redis 7.0.0, the
SORT_RO variant was introduced in order to allow SORT behavior in read-only replicas without breaking compatibility on command flags.
See original SORT for more details.
SORT_RO mylist BY weight_*->fieldname GET object_*->fieldname
Array reply: a list of sorted elements.