GraphQL vs OpenAPI: What are the differences?

Introduction:

In website development, two popular technologies used for designing APIs are GraphQL and OpenAPI. While both offer solutions for building APIs, there are key differences between them. This Markdown code will outline these differences in a clear and concise manner.

1. Data fetching: GraphQL allows clients to specify exactly what data they need and receive only that, reducing over-fetching and under-fetching of data. In contrast, OpenAPI follows a traditional RESTful approach where clients can only retrieve the pre-determined data structure defined by the server.

2. Schema-driven vs documentation-driven: GraphQL is schema-driven, meaning the schema acts as the single source of truth for clients and servers. Clients can easily discover and understand the API's capabilities through the schema. On the other hand, OpenAPI is documentation-driven, requiring developers to write and maintain detailed documentation to describe the API's structure, operations, and parameters.

3. Flexible querying: GraphQL allows clients to query multiple resources and related data in a single request, minimizing the number of round trips to the server. OpenAPI, on the other hand, requires clients to make separate requests for each resource, which can result in increased network overhead and latency.

4. Versioning: GraphQL does not require explicit versioning as the schema is designed to evolve over time without breaking changes. Clients can request specific fields and modify the query as needed without depending on a specific version. In contrast, OpenAPI typically relies on versioning to handle modifications, and clients must update their requests to match the specific API version.

5. Strong typing: GraphQL enforces a strong type system for APIs, enabling clients to validate their queries against the schema. This improves development efficiency by catching errors early. OpenAPI, on the other hand, allows for looser typing and does not provide the same level of validation against the API's structure and data types.

6. Backend control: GraphQL empowers clients to control the shape and structure of the data they receive, abstracting away the backend implementation details. This provides more flexibility and reduces the need for backend changes when evolving the API. In contrast, OpenAPI puts more control on the backend, specifying the data structure and limiting the flexibility for clients to request only the necessary data.

In Summary, GraphQL offers flexible data fetching, schema-driven design, and versionless querying, while OpenAPI is documentation-driven, requires separate requests for each resource, and relies on explicit versioning.