db={"Users":[{"_id":1,"name":"user1","posts":[1,2,3]},{"_id":2,"name":"user2","posts":[1,]},{"_id":3,"name":"user3","posts":[1,3]},],"Posts":[{"_id":1,name:"Post1","is_active":false,},{"_id":2,name:"Post2","is_active":true,},{"_id":3,name:"Post3","is_active":true,}]}

db.Users.aggregate([{$lookup:{from:"Posts",let:{postIds:"$posts",},pipeline:[{$match:{$expr:{$and:[{$in:["$_id","$$postIds"]},{$eq:["$is_active",true]},]}},},{$project:{_id:1}}],as:"posts"}},{$match:{$expr:{$gt:[{$size:"$posts"},0]}}}])