How to Process Azure Cosmos DB Change Streams in Parallel with Java (and Stop Leaving Throughput on the Table)

You have a Cosmos DB collection with dozens of physical partitions and millions of documents. You need to migrate them or stream changes in real time to another system. You open a single change stream cursor and watch it crawl through one partition at a time, burning hours that should take minutes. The bottleneck isn't Cosmos DB. It's the single-threaded cursor you're reading with. Cosmos DB shards data across physical partitions, but a vanilla change stream reads them sequentially. Every partit