db={"users":[{"searchFilter":{"remote":0,"data":[{"country":"DEU","searchActive":false,"postalCode":"123","available":{"$toDate":1664955924380}},{"country":"DEU","searchActive":false,"postalCode":"850","available":{"$toDate":1667165151744}}]}}],jobs:[{"postalCode":"12345","country":"DEU",}]}

db.users.aggregate([{$match:{}},{$unwind:"$searchFilter.data"},{$lookup:{from:"jobs",let:{postalCode:"$searchFilter.data.postalCode"},pipeline:[{$match:{$expr:{$eq:[{"$substr":["$postalCode",0,{"$strLenCP":"$$postalCode"}]},"$$postalCode"]}}}],as:"searchFilter.data.jobs"}},{$match:{"searchFilter.data.jobs.0":{$exists:true}}},{$group:{_id:"$_id",searchFilter:{$push:"$searchFilter.data"},remote:{$first:"$searchFilter.remote"}}}])