db={persons:[{"_id":"02a33b9a-284c-4869-885e-d46981fdd679","context":{"email":"someemail@gmail.com","firstName":"John","lastName":"Smith","company":["e2467c93-114b-4613-a842-f311a8c537b3"],},},],companies:[{"_id":"e2467c93-114b-4613-a842-f311a8c537b3","context":{"name":"Coca Cola","image":"someimage",},}]}

db.persons.aggregate([{$addFields:{name:{$concat:["$context.firstName"," ","$context.lastName"]},companyId:{$arrayElemAt:["$context.company",0]}}},{$lookup:{from:"companies",let:{company_id:{$arrayElemAt:["$context.company",0]}},pipeline:[{$match:{$expr:{$eq:["$_id","$$company_id"]}}},{$project:{name:"$context.name"}}],as:"company"}}])