https://github.com/10gen/mongo/blob/78d61a2f2ce86497c066ef1a969001d9cba150ad/src/mongo/db/modules/enterprise/src/streams/exec/s3_emit_operator.cpp#L498-L533

We currently increment stats before calling PutObjectAsync. Instead, we should wait for the callback to increment stats for S3 $emit to more accurately report the number of successfully emitted documents. In the event of failures, we're counting documents that failed to be emitted in the `numOutputDocuments` count.