REST vs SOAP vs GraphQL vs gRPC — Interview Notes for Backend Engineers

In this account, I will discuss the differences between REST, SOAP, GraphQL, and gRPC, as well as the key factors interviewers look for when choosing an API style. REST APIs are based on resources (nouns) and HTTP methods (verbs). They use a stateless approach with safe and idempotent requests, and provide representations usually in JSON format.

When choosing an API style, consider if the API is public or mobile, if there is a need for different client slices, if over-fetching is a concern, or if the API will be used internally for service-to-service communication.

REST APIs are the most common choice for public or mobile APIs due to their browser-friendly nature and natural caching with GET requests. They work well for public or mobile APIs and are easy to implement with JSON payloads. However, for internal service-to-service communication, gRPC may be more suitable due to its low latency and typed generated clients.

SOAP APIs are best for enterprise partner contracts or when one side requires a contract, such as in finance or government integrations. GraphQL APIs are an option when different clients require varying slices of data, as they allow clients to request only the necessary fields. Lastly, WebSockets can be used for live updates after the initial load, but are better suited for private APIs rather than public mobile APIs.

In summary, when deciding between REST, SOAP, GraphQL, and gRPC, consider the API's intended use, the need for different client requirements, and the level of internal service-to-service communication. For public or mobile APIs, REST is often the best choice, while SOAP is more appropriate for enterprise partnerships. GraphQL is useful for clients needing specific data fields, and gRPC shines for internal, high-performance service-to-service communication.