REST endpoints typically return a specific set of data that you can optimize queries for. Whereas the GraphQL endpoint must handle arbitrary queries which will require some logic to prevent N+1 queries on the related tables or even resolve to other data sources.
REST endpoints typically return data I don't need. For example, the twitter REST API `/1.1/users/show.json?screen_name=twitterdev` it will show me the last tweet for the user. Presumably this involves perhaps waiting for tweet service when the client may not even want the tweet. A GraphQL client can be more explicit about what edges to select.
There are specs like jsonapi that solve this problem. I’ve never been entirely convinced that GraphQL is better than actual REST, even if it’s better than most of the APIs people call RESTful
JSON:API provides some of the same functionality as GraphQL, like specifying which fields and nested resources you want, but at that point you’re going to have the same problems with ensuring good performance with any combination of included fields and relationships.
Yes, the advantage of a GraphQL endpoint is you can ask for a variety of things and the tradeoff is potential performance issues for unforeseen queries doing N+1s or something.
If you control the API and know all the use cases for a REST endpoint, the advantage is predictable performance characteristics and the tradeoff is flexibility.
It all depends on what you need (and maybe what tools you're using to mitigate GraphQL resolver problems).
> REST endpoints typically return a specific set of data that you can optimize queries for
You mean when someone creates a REST API he magically knows in advance how it will be used and writes a bunch of specific, optimized endpoints and queries such as "/magic-endpoint/" which returns 20 blogposts with their comments?
I don't think so. And even if that were true, the same could easily be done with GraphQL.
It's not magic, you would design it in advance so you know what you're querying by and what you're returning in the payload. Typically you'd probably separate it into two endpoints `/blogposts` and `/blogposts/:id/comments`, but there are many ways to approach the problem. These days JSON:API is pretty popular for creating standard interfaces.
GraphQL allows ad-hoc queries of unlimited complexity and recursion
> If you know in advance what will be queried then you can create an optimized query for it.
No. In general you don't know what will be queried. And that's the reason why most GraphQL implementations end up using just a small predefined set of "persisted queries" (that is, REST with extra steps).
I think you misunderstand. You can write very restricted queries that mirror REST routes 1:1. No need for persisted queries.
Persisted queries enter the game when you define a query that potentially can become very complex and deep and then want to restrict the complexity in specific ways. But that is not required if you just want to mirror a RESTful API.