[{_id:ObjectId("65d5e666deda15bb37f308fe"),deleted:false,fields:{"uuid":"some_uuid","employees":[{"first_name":"Anna"},{"first_name":"Bob"},{"first_name":"Carol"},{"first_name":"Dave"}]}}]

db.collection.aggregate([{$match:{"fields.uuid":"some_uuid"}},{$set:{"fields.employees":{$sortArray:{input:"$fields.employees",sortBy:{"first_name":-1}}}}}])