Rsrc is tiny. Weighing in at 7.5k (2.6k gzipped) means it won't take up too many precious bits in your bundle. With the exception of ensuring polyfills for your target environments and an optional LRU cache, there's no additional dependencies required for a production-ready setup.
Rsrc doesn't impose many opinions of its own. For the most part, it's a lightweight wrapper around common, battle-hardened APIs you probably already know and love - ES6 maps, fetch, and promises. The API encourages the colocation of data fetching alongside the presentational components that depend on it.
Rsrc doesn't require an all-in transformation of your codebase. No configuration or scaffolding is needed to get up and running, so the initial barrier is low. More importantly, with less boilerplate compared to traditional flux approaches, the overall lines of code to maintain are reduced as well.