Database
[{"deviceId":"1106","orgId":"5ffe9fe1c9e77c0006f0aad3","values":[{"paramVal":105.0,"dateTime":ISODate("2021-05-05T09:18:08.000Z")},{"paramVal":110.0,"dateTime":ISODate("2021-05-05T09:18:08.000Z")},{"paramVal":115.0,"dateTime":ISODate("2021-05-05T10:18:08.000Z")},{"paramVal":125.0,"dateTime":ISODate("2021-05-05T11:18:08.000Z")},{"paramVal":135.0,"dateTime":ISODate("2021-05-05T12:18:08.000Z")}]}]
Query
db.collection.aggregate([{$set:{values:{$slice:["$values",-2]}}}])