Hyperfiddle isolates your web clients from I/O, so your code can stay pure. If React.js is managed DOM, Hyperfiddle is managed network and database. This enables a new kind of composable primitive for constructing web software, with paradigm-changing implications. The hardest part of web dev is I/O: data sync between database, various services, UI and then back to the database. An async, slow, failure-prone concern wired throughout the full stack, and the reason why we all code the same web boilerplate over and over again, year after year – a collosal, industry-wide failure to abstract.