GraphQL

What is GraphQL?

GraphQL is a query language for APIs and a runtime for fulfilling those queries with your existing data. It was developed by Facebook in 2012 and open-sourced in 2015.

Unlike REST, which exposes multiple endpoints for different resources (e.g., /users, /posts, /comments), GraphQL typically exposes a single endpoint (usually /graphql). Clients send a query describing exactly the data structure they need, and the server returns a JSON response matching that structure.

Core Concepts

Schema (SDL): The contract between client and server. It defines the types and relationships.

Query: A read-only fetch operation (equivalent to GET).

Mutation: A write operation (equivalent to POST/PUT/DELETE).

Subscription: A generic long-lived connection for real-time updates.

Resolver: Functions that retrieve the actual data for each field in the schema.

Code Example: The Schema

In GraphQL, you define types in the Schema Definition Language (SDL):

Comparisons: GraphQL vs. REST

Feature	REST	GraphQL
Endpoints	Multiple (resource-based)	Single (usually `/graphql`)
Data Fetching	Fixed structure (Over/Under-fetching)	Client defines exact structure
Versioning	v1, v2 URL prefixes	Evolution via deprecation (schema-first)
Caching	Built-in HTTP caching	Requires specialized setup (e.g. Apollo)
Performance	Larger payloads, simple processing	Smaller payloads, complex server processing

When to Use GraphQL?

Mobile Applications: Minimizes bandwidth by fetching only required fields. Solves the "waterfall" problem of chaining multiple API calls.

Microservices Aggregation: A GraphQL "Gateway" can stitch together data from multiple backend microservices into a single unified API for the frontend.

Rapid Iteration: Frontend teams can modify queries to get new data without waiting for backend teams to build new endpoints.

Debugging GraphQL in Apidog

Apidog provides a first-class GraphQL client experience, including schema introspection and docs generation.

1. Creating the Request

Create a new endpoint.

Set the method to POST.

In the Body tab, select GraphQL.

2. Intelligent Query Editing

Leverage Apidog's introspection capabilities:

Fetch Schema: Click Fetch Schema to download the type definitions from the server.

Auto-Completion: Type within the editor to see available fields, types, and arguments.

Validation: Real-time error checking against the schema schema.

3. Using Variables

Apidog supports separating query logic from data values using Query Variables.

Query:

Variables (JSON):

{
  "id": "123"
}

See details GraphQL

Key Takeaways

Single Endpoint: GraphQL uses a single URL (e.g., /graphql) for all data interactions.

Client-Spec: Clients define exactly what data they need, preventing over-fetching and under-fetching.

Strongly Typed: The Schema Definition Language (SDL) ensures a strict contract between client and server.

Introspection: Apidog can "read" your GraphQL schema to provide auto-completion and documentation automatically.

Continue with → gRPC

What is GraphQL?#

Core Concepts#

Code Example: The Schema#

Comparisons: GraphQL vs. REST#

When to Use GraphQL?#

Debugging GraphQL in Apidog#

1. Creating the Request#

2. Intelligent Query Editing#

3. Using Variables#

Key Takeaways#