Currently for sharded clusters Debezium opens a connection to each shard's replica set directly for snapshot and streaming.
While this approach should allow for a higher throughput due to utilised parallelism,[ it is not recommended by MongoDb|https://www.mongodb.com/docs/manual/sharding/#connecting-to-a-sharded-cluster]
We should provide a way to utilise proper connection via mongos instance. However this solution should be backwards compatible – at least for the lifespan on 2.x release line.
Additionally this will allow support of incremental snapshotting for sharded deployments as well as total ordering of captured change events.