Database
[{"_id":ObjectId("60112357e06d453f0545f0b4"),"glass":"7835","ts":ISODate("2021-01-27T08:24:55.696Z"),"val":{"litr":0.21405}},{"_id":ObjectId("60112361e06d453f0545f0b5"),"glass":"7835","ts":ISODate("2021-01-27T08:25:05.694Z"),"val":{"litr":0.215108}},{"_id":ObjectId("60112393e06d453f0545f0ba"),"glass":"7835","ts":ISODate("2021-01-27T08:25:55.698Z"),"val":{"litr":0.224469}}]
Query
db.collection.aggregate([{"$match":{"glass":"7835"}},{$sort:{"ts":-1}},{$limit:1}])