From what I can tell, Relay and Apollo serve as an implementation of functions you'd need to write to organize the fetching of your data on the client side. It

From what I can tell, Relay and Apollo serve as an implementation of functions you'd need to write to organize the fetching of your data on the client side. It turns things like "oh, in componentDidMount I need to fetch a route and update that data inside the store I'm using" into "Hey Relay this component needs this data before it loads". Relay I think is a more opinionated and heavier weight option, with the benefit provided being that it intelligently aggregates queries based off fragments and allegedly handles caching (minus invalidation, so you could argue that it doesn't really handle it ;) ) Fwiw in the project I'm working on now we judged that the extra complexity of a data fetching layer like Relay or Apollo wasn't worth it for us. We may have come to a different conclusion with a different project. Ymmv