Swarm is reactive data sync middleware that uses CRDT (Commutative Replicated Data Types) to enable total caching and incremental synchronization of data across devices. It allows for real-time background syncing of versioned data while detecting new and previously seen changes, enabling offline work, caching, and prefetching. This provides a huge improvement to the user experience by eliminating loading stalls and supporting intermittent connections. While building a total caching system from scratch requires significant effort, Swarm implements CRDTs to achieve this faster than the theory is developed.