Definition
GraphQL is an open-source query language and runtime for APIs developed by Facebook. It allows clients to request exactly the data they need, no more and no less. Unlike REST, where multiple endpoints may be required, GraphQL uses a single endpoint to provide structured responses tailored to each query.
This approach reduces over-fetching and under-fetching of data, making applications more efficient and responsive. It is widely used in modern web and mobile applications where performance and flexibility are critical.
Advanced
At an advanced level, GraphQL defines data with a strong type system, using schemas to describe the available queries, mutations, and subscriptions. Queries are used to read data, mutations to modify data, and subscriptions to handle real-time updates.
GraphQL works independently of databases and can aggregate data from multiple sources, including SQL databases, NoSQL systems, and third-party APIs. Advanced implementations include query batching, caching, and federation to handle distributed architectures.
Why it matters
- Gives clients full control over the data they request.
- Reduces network usage by eliminating redundant data transfers.
- Simplifies integration with multiple data sources.
- Supports real-time functionality through subscriptions.
Use cases
- Powering mobile applications with optimised data fetching.
- Building dashboards that combine multiple APIs into one interface.
- Supporting e-commerce platforms with dynamic product data queries.
- Delivering personalised content and recommendations.
Metrics
- Query response time and server load.
- Efficiency in reducing over-fetching compared to REST.
- Error rates and schema validation success.
- Adoption rates among frontend and backend teams.
Issues
- Requires careful schema design to avoid complexity.
- Potential performance issues with deeply nested or unoptimized queries.
- Lacks built-in caching and versioning compared to REST.
- Steeper learning curve for teams new to GraphQL concepts.
Example
A news app uses GraphQL to fetch article data. The client requests only the headline, author, and publication date rather than the full article body. This targeted approach reduces data transfer and improves load times, resulting in a smoother user experience.