db={Company:[{_id:1}],referralLinks:[{companyId:1,categoryId:1,link_status:"Approved"},{companyId:1,categoryId:1,link_status:"Other"}],categories:[{_id:1}]}

db.Company.aggregate([{$lookup:{from:"referralLinks",let:{company_id:"$_id"},pipeline:[{$match:{$expr:{$and:[{$eq:["$$company_id","$companyId"]},{$eq:["$link_status","Approved"]}]}}}],as:"referrals"}},{$lookup:{from:"categories",localField:"referrals.categoryId",foreignField:"_id",as:"categories"}}])