GraphQL vs REST: When to Use Each

REST (Representational State Transfer) has been the king of APIs for 20 years. GraphQL is the challenger developed by Facebook. Which one should you choose?

The Problem with REST: Over-fetching and Under-fetching

Imagine you need to show a user's name and their last 3 tweets. In REST:

1. GET /users/1 (Returns all user info: name, email, birthday, address... -> Wasted Data/Over-fetching)
2. GET /users/1/tweets (Returns all tweet info -> Wasted Data)
3. You make two network round-trips.

The GraphQL Solution

You send ONE query asking for exactly what you want:

query {
  user(id: 1) {
    name
    tweets(limit: 3) {
      text
    }
  }
}

The server returns exactly that JSON structure. No more, no less. This saves massive bandwidth on mobile devices and speeds up the UI.

The Trade-offs

• Complexity: GraphQL requires a heavier backend setup (Resolvers, Schema definition). Simple CRUD apps are often faster to build with REST.
• Caching: HTTP caching (ETags, CDN) works out of the box with REST because URLs are unique. GraphQL uses a single URL (POST /graphql), making caching at the network edge much harder.
• Security: GraphQL allows clients to ask for "everything". You must implement strict Query Depth Limiting to prevent malicious users from DDoSing all your database relationships in one nested query.

Verdict: Use GraphQL for complex, data-rich frontends (like Dashboards or Social Feeds). Stick to REST for simple services or public APIs.