Ah but that's the beauty of GraphQL, a query can actually fetch data from several systems: the db, the cache, the search engine, etc. It's all abstracted away.

But let's say you have a timeout, and they have a retry, then suddenly, your server is now spammed by all the clients retry again and again a query that worked a week ago, but today is too heavy because of a tiny change nobody noticed.

And even if it's not the case, you can now break the client at any time because they decide to use a feature you gave them, but that you actually can't deal with right now.

To be clear, the main thing that's abstracted away are server round-trips and client-side joins. REST APIs can fetch data from different systems too.

Sure but queries are crafted in the client, that may know nothing about this, while a rest api, the requests are restricted and the queries are more likely under control of the server, which mean the backend will likely decide what fetches what and when.

It takes a lot of work to actually ensure all possible combinations of graphql params hit exactly what you want in the backend, and it's easy to mess with it in the frontend.

I'm not that much into GraphQL but I vaguely remember libraries that provide some kind of atteibutes you apply to entities/loaders and then pre-execution an estimated cost is calculated (and aborted if over a specified threshold).

API Platform for PHP is one of those graphql implementations that has a query cost limiter built in (it's binary, it just rejects queries that go over your configured complexity threshold). Shopify's graphql api is even fancier, where every query costs X amount of a limited number of "credits". The structure of gql itself makes costs easier to estimate (you have as many joins as you have bracket pairs, more or less), and some servers can recognize a directive in the schema to declare the "real" cost.

That's sort of my expectation too -- it would be nuts to provide a user facing system without bounds of some sort.

There’s a free query depth. There’s ways to do query cost but federating that then becomes really annoying. Coming from the security side, there’s always a long curve of explaining and an even longer curve of mitigating.

I always am happy when I get an elegant query working. Often however I just find I wasted time looking for a clean 1 query solution when iteration by caller was the only solution.