GraphQL vs REST — what are the trade-offs, and when would you choose GraphQL?

Question

"Our mobile app makes 5 API calls to render one screen. GraphQL could reduce to 1. Worth the complexity?"

Interview OS Community · Accepted Answer

| Aspect | REST | GraphQL |
|--------|------|---------|
| Endpoints | Multiple | Single (/graphql) |
| Over-fetching | Common | Eliminated |
| Under-fetching | Multiple requests | Single query |
| Caching | HTTP caching (easy) | Requires Apollo Cache |
| Versioning | /v1, /v2 | Schema evolution |

**GraphQL wins**: Mobile (minimize data), complex nested data, multiple client types.
**REST wins**: Simple CRUD, file upload, HTTP caching, team unfamiliarity.

## N+1 in GraphQL
```graphql
query { users { posts { comments { author } } } }
```
Each level = separate DB queries. Fix with DataLoader (batch + cache).

Interview OS

GraphQL vs REST — what are the trade-offs, and when would you choose GraphQL?

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Suggested Solution

N+1 in GraphQL

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Aspect	REST	GraphQL
Endpoints	Multiple	Single (/graphql)
Over-fetching	Common	Eliminated
Under-fetching	Multiple requests	Single query
Caching	HTTP caching (easy)	Requires Apollo Cache
Versioning	/v1, /v2	Schema evolution