Database
[{date:"2022-09-25",user:"A"},{date:"2022-09-25",user:"A"},{date:"2022-09-25",user:"B"},{date:"2022-09-26",user:"A"}]
Query
db.collection.aggregate([{$group:{_id:"$date",users:{$addToSet:"$user"},entries:{$sum:1}}},{$project:{date:"$_id",entries:1,uniqueUsers:{$size:"$users"},_id:0}}])