The document discusses how Salesforce moved sharing operations to a parallel architecture to improve performance and scalability. Sharing tables control access at the record level but were previously processed sequentially, limiting performance. Salesforce now enqueues sharing jobs in parallel batches which are processed asynchronously by multiple applications. This approach provides 4-5x faster performance for sharing operations like creating rules in production environments, and up to 15x faster in testing. The parallel architecture is being rolled out gradually and more optimizations are planned to support continued scalability.