PourOver is an attempt to standardize an efficient and extensible model of client-side collection management, weakening reliance on server-side collection operations. Even on modern networks with beefy machines, the roundtrip to a backend is irredeemably slow for responsive UIs. Users aren’t encouraged to explore when every manipulation triggers a half-second pause. With PourOver, the server-trip bottleneck is gone because collection operations are done on the client. The hardest limitation becomes render speed, much simpler to improve upon than the latency of the internet.