The subject technology receives an operation to perform on an external data source accessible via a network, the external data source being hosted by an external system separate from a network-based database system. The subject technology determines a set of shards corresponding to the external data source. The subject technology determines a set of offsets of each shard of the set of shards. The subject technology, based on the set of shards and the set of offsets, performs the operation on the external data source. The subject technology provides an indication that the operation is complete.