Currently debezium openes change stream directly on each shard's primary, however this approach cannot guarantee the order of all cdc events across shrads. A possible solution is to use the monogs change stream (https://www.mongodb.com/docs/manual/administration/change-streams-production-recommendations/#sharded-clusters)

https://debezium.zulipchat.com/#narrow/stream/302529-users/topic/can.20debezium.20order.20events.20across.20shards