> db.createCollection( "ts" , { timeseries: { timeField: "time" , metaField: "meta" , granularity: "minutes" }}) > db.ts.insertMany([{time: new Date(), meta: {key: 2, val: 0}, val: 42, key: 1},{time: new Date(), meta: {key: 1, val: 0}, val: 43, key: 1}]) single predicate with non-consts > db.ts.aggregate({$match: {$expr: {$lt: [ "$meta.val" , "$val" ]}}}) correctly returns both docs from the collection two const predicates, combined with $and, > db.ts.aggregate({$match: {$expr: {$and: [{$lt: [ "$meta.val" ,42]}, {$eq: [ "$meta.key" ,1]}]}}}) correctly returns one matching doc from the collection two predicates, one of them non- const > db.ts.aggregate({$match: {$expr: {$and: [{$lt: [ "$meta.val" , "$val" ]}, {$eq: [ "$meta.key" ,1]}]}}}) raises error: "errmsg" : "Failed to optimize pipeline :: caused by :: createComparisonPredicate() does not handle metadata predicates: 0xAAAB14AD4640" , "code" : 6707200 two non- const predicates, split across two $match stages > db.ts.aggregate([{$match: {$expr: {$lt: [ "$meta.val" , "$val" ]}}}, {$match: {$expr: {$eq: [ "$meta.key" , "$key" ]}}}]) correctly returns one matching doc from the collection