Field Selection

One reason teams reach for GraphQL is over-fetching: an endpoint returns 30 fields when the client needs 3. REST can offer the same control with two simple query parameters.

Sparse fieldsets

Let the client list the fields it wants with ?fields=:

GET /articles?fields=id,title

The server returns only those keys. This shrinks payloads for mobile clients and list views, and documents intent. Always include the resource’s identifier even if not requested, so responses stay addressable.

Expanding related resources

By default, link to related resources rather than embedding them. When a client wants them inline, let it opt in with ?expand=:

GET /articles/42?expand=author

Without expand, author is a reference ({ "id": 7, "href": "/users/7" }); with it, the author object is embedded. This keeps the default response small while avoiding an extra round trip when the client genuinely needs the related data.

Projecting fields in code

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function project(obj, fields) { if (!fields) return obj; const wanted = new Set(['id', ...fields.split(',')]); // always keep id return Object.fromEntries(Object.entries(obj).filter(([k]) => wanted.has(k))); } const article = { id: 42, title: 'Hello', body: 'long...', views: 1200, authorId: 7 }; console.log(project(article, 'title,views'));

🌐 Small default, opt-in detail

Design the default response to be lean and link out to related resources. Then give clients fields to trim further and expand to pull related data inline when they need it. You get GraphQL-like flexibility without giving up REST’s caching and simplicity.

What does `?fields=id,title` request?

Only the id and title fields in the response Sort by id then title Filter where id equals title Two separate resources

What is the purpose of an `?expand=author` parameter?

Delete the author Embed the related author inline instead of just linking to it Sort by author Paginate authors

Why always include the identifier even if not in `fields`?

To make the payload bigger So the returned object stays addressable/identifiable HTTP requires it To enable sorting

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