Key Points
- GraphQL is an open-source API query language. It enables clients to request exactly the data they need through a single endpoint.
- A GraphQL API is built on components such as schemas, resolvers, queries, and mutations, which define what data can be accessed, how it is retrieved, and how it can be modified.
- GraphQL consolidates multiple data sources into one endpoint that responds to structured, client-defined queries.
- GraphQL is best suited for complex, flexible data environments such as mobile applications, internal dashboards, and customer portals.
- GraphQL introduces various considerations around security, including authentication enforcement, query depth limiting, introspection controls, and schema governance.
- Organizations with simple, predictable resource patterns or limited IT governance capacity may find that REST meets their needs with less operational overhead.
GraphQL is a query language that’s used to build APIs that can give applications the ability to request data from backend systems. Instead of returning a fixed response from a predefined endpoint, GraphQL allows the client to describe the data it needs.
This flexibility can reduce unnecessary data transfer and simplify API interactions. However, it’s not a perfect solution since it also introduces operational considerations. IT teams, developers, and automation teams need to understand how GraphQL queries, schemas, mutations, and resolvers work before adopting or supporting GraphQL APIs.
What is GraphQL?
GraphQL is an open-source query language and runtime specification for APIs. It allows clients to request specific fields defined in a schema. A GraphQL API typically exposes a single endpoint where clients submit structured queries, and the API retrieves the requested data from underlying systems.
It’s commonly used when applications need flexible access to data or when clients need to use different response structures. Some applications for GraphQL include:
- Web applications
- Mobile applications
- Internal dashboards
- Customer portals
- API aggregation layers
- Any system that combines data from multiple backend services
How does a GraphQL API work?
A GraphQL API acts as an interface between clients and backend systems. It typically exposes a single endpoint where clients submit queries, while the API retrieves and combines data from one or more underlying data sources before returning a response.
A GraphQL API depends on various core components to function.
- Schema: This is the definition of a GraphQL API. It specifies the available data types, fields, relationships, and the operations (queries and mutations) that clients can execute.
- Type System: This defines the data types and structures used by the GraphQL schema, specifying how data is represented and related within the API.
- Query: This is the structured request that a client sends to a GraphQL API to retrieve data. The query typically reflects the structure of the response that the client expects to receive.
- Resolver: This serves as your data fetchers, connecting the data defined in the schema to the data available in data sources. This way, the API can return the correct value the client asked for.
- Mutation: This allows you to change data in the data sources through the GraphQL API, which includes creating, updating, or deleting data.
- Endpoint: This is the API access point where clients submit GraphQL queries. The GraphQL API processes those queries and returns the resulting response to the client.
When using a GraphQL API, the schema and type system define the available data structures and operations. A client submits a query to the GraphQL endpoint, and resolvers retrieve or generate the requested data. When a client needs to perform an operation that changes the application state, it uses a mutation, which is executed by the GraphQL API.
What does a GraphQL query do?
A GraphQL query is a message from the client that tells the API exactly what it has to do. For example, a mobile application requires the username, email address, and assigned devices. To get that information, it will send a query that requests all this information in one message. If they only need the username and email address, it will only put those fields in the query.
Using GraphQL queries can help reduce over-fetching by allowing clients to request specific fields, and may reduce under-fetching by enabling related data to be retrieved in a single query. It also prevents client-side filtering caused by overly broad API responses.
GraphQL in comparison
GraphQL vs REST
A Representational State Transfer (REST) API organizes resources across multiple endpoints, with each endpoint typically exposing a predefined resource structure. GraphQL, on the other hand, typically exposes a query interface that allows clients to request specific fields from one or more underlying data sources.
REST is generally a more server-driven approach, while GraphQL is generally more client-driven. REST can be a good fit for simpler and more predictable data access patterns, while GraphQL is often beneficial when clients require flexible access to related data or different response structures.
GraphQL vs SQL
While GraphQL and SQL may be confused because they both involve queries, they’re very different things. SQL is a query language for relational databases. It’s used to retrieve, modify, and manage the data inside a database. On the other hand, GraphQL is a query language for APIs. It defines how clients can request data from an API layer, some of which may be, but are not necessarily connected to an SQL database.
GraphQL vs Microsoft Graph API
Despite their similar names, GraphQL and Microsoft Graph API are not related. GraphQL is a general query language used on APIs, while the Microsoft Graph API is Microsoft’s unified API that allows users to access Microsoft 365 and other related cloud service data.
Benefits of GraphQL
GraphQL has many benefits, including:
- Flexible data retrieval: Clients can request only the data they need at the time.
- Fewer API round-trips: Related data can often be retrieved through a single query, which may reduce the number of API requests required by the client.
- Strong schema structure: The API’s schema defines the available data clearly.
- Better frontend flexibility: Different clients can request different data shapes, according to their needs.
- API evolution: Fields can be added without having to create a new endpoint every time you change something.
- Aggregation support: A GraphQL API can provide a unified interface for accessing data from multiple backend systems.
GraphQL limitations and operational considerations
GraphQL is not a perfect solution. Here are some limitations and things you need to consider before using it:
- For security reasons, you need to make sure that users and systems are properly verified before they access the API.
- When making flexible queries, you must ensure that you have safeguards in place to ensure that the user can’t access information they’re not supposed to.
- You need to have a way to control excessive or abusive query behavior to protect your organization’s data.
- GraphQL may require specific caching strategies that you need to learn before implementation.
- Administrators should track query performance, errors, latency, and usage patterns.
- Before making any changes to the API schema, you need to make sure they don’t break your clients or expose unnecessary data.
- You need to have visibility into what queries are being run and how they’re performing.
When to use GraphQL
GraphQL is a good fit when your client needs different data shapes from the same API or if your applications frequently need related data from multiple sources. If your backend data comes from multiple sources, or you need to reduce your payload size. At the end of the day, GraphQL gives clients flexibility by allowing them to request different fields and response structures without requiring API changes for every use case.
However, it’s not a perfect solution. If you’re working with predictable resource patterns, REST can meet your needs. If you still have a small operation, your IT team might not have the capacity to keep up with schema governance and query controls. GraphQL is for complex and flexible queries, and if you don’t need that, it may add an unnecessary layer of complexity to your operations.
Streamline data queries with GraphQL
GraphQL is a query language for APIs. It allows clients to request GraphQL, giving clients flexibility by allowing them to request different fields and response structures without requiring API changes for every use case.
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