JSON API Standard - json-api

Question

I have a doubt what is a better option when using json api standard and communication between backend and frontend. I need only one attribute from author association - „username” and other stuff should be hidden for user that fetch this
Case a)
data: [
{
id: „100”,
type: „resource1”,
attributes: {…},
relationships: {author: {data: {id: „10”, type: „author”}}}
}
],
included: [
{
id: „10”,
type: „author”,
attributes: {username: „name”},
relationships: {resources1: {data: [{id: „100”, type: „resource1”}]}}
}
]
Case b)
data: [
{
id: „100”,
type: „resource1”,
attributes: {authorName: „name”, …},
relationships: {author: {data: {id: „10”, type: „author”}}}
}
],
included: []
Case a) looks semantic but there serve much more information in payload
Case b) is faster to get what I want from author (one attribute „username” and this is added in additional attribute: „authorName”), so also don’t need to pleas with associations in frontend side.
Any thoughts which is better practice and why?

Answer 1

Strictly speaking both case a and case b are valid per JSON:API specification.
In case a username is an attribute of author resource. In case b authorName is an attribute of resource1. author resource may have a username attribute in case b as well. In that case you have duplicated state.
I would recommend to only use duplicated state if you have very good reasons. Duplicated state increases complexity - both on server- as well as client-side. Keeping both attributes in sync comes with high costs. E.g. you need to update a client that resource1 changed after a successful update request, which affected the username of author resource. And the client need to parse that response and update the local cache.
There are some reasons, in which duplicating state pays off for good reasons. Calculated values, which would require a client to fetch many resources to calculate them, is a typical example. E.g. you may decide to introduce a averageRating attribute on a product resource because without a client would need to fetch all related ratings of a product only to calculate it.
Trying to reduce payload size is nearly never a good reason to accept the increased complexity. If you consider compressing and package sizes at network level, the raw payload size often doesn't make a big difference.