What is GraphQL?

GraphQL: definition and importance

An API is the interface through which programs exchange data. GraphQL is an approach in which the client describes in the request exactly which fields it needs—and the server delivers only those. The data is treated as a connected network (“graph”) of objects, such as customer, orders and items.

GraphQL is not a database and no substitute for business logic, but a unified layer in front of it. Behind it can sit databases, other interfaces or legacy systems. Many platforms now offer GraphQL, including GitHub and Shopify for their interfaces, and many companies use it for their own applications.

How GraphQL works

The server publishes a schema that describes all available types, fields and relationships. Clients usually send a query, to read data, or a mutation, to change data, via HTTP POST to a single endpoint. For real-time updates there are additionally subscriptions.

An example: for an overview, an app needs only a customer’s name and the numbers of their last three orders. A single query fetches exactly that. With a classic REST API, several calls would often be needed, and they would return more fields than necessary (under- and overfetching).

Real-world example: one data set, many interfaces

A furniture manufacturer runs an online store, a dealer portal and a field-service app. All three use the same product data but need different slices: the store needs images and descriptions, the dealer portal purchase prices, and the app only item number and stock level. Previously there were three separate interfaces for this.

With GraphQL, the team builds a shared layer from which each interface queries exactly the fields it needs. New requirements often need no new interface, just an adjusted query. Permissions are checked on the server, so the dealer portal may see purchase prices while the public store may not.

Benefits, limits and common mistakes

The benefits of GraphQL are less data traffic, a self-documenting schema and fast development of frontends. Against that stand limits: caching is more laborious than with REST, open-ended queries can put heavy load on the server, and getting started requires more know-how. Typical mistakes:

• Using GraphQL although a simple REST API would be perfectly sufficient
• No limits on query depth and complexity, so single queries overload the server
• Checking permissions only in the interface instead of on the server for every field
• Exposing schema details and verbose error messages without protection
• Ignoring N+1 database queries on the server

What businesses should look out for

Whether GraphQL or REST fits depends on the use: many different clients and nested data favor GraphQL, simple interfaces and easily cacheable data favor REST. Nano Concepts builds both variants, secures them (authentication, limits, monitoring) and documents the API so that partners and frontend teams can start using it quickly.