Database
[{_id:1,blogName:"abc",posts:[{_id:"6066495f347bb812fd6dc701",kind:"PhotoPost1",createdAt:"2021-04-01T22:29:51.815Z",updatedAt:"2021-04-01T22:29:51.815Z",},{_id:"6066495f347bb812fd6dc702",kind:"PhotoPost2",createdAt:"2021-04-01T22:29:51.815Z",updatedAt:"2021-04-01T22:29:51.815Z",},{_id:"6066495f347bb812fd6dc703",kind:"PhotoPost3",createdAt:"2021-04-01T22:29:51.815Z",updatedAt:"2021-04-01T22:29:51.815Z",}]},]
Query
db.collection.aggregate([{$match:{blogName:"abc"}},{$unwind:"$posts"},{$replaceRoot:{"newRoot":"$posts"}}])