GraphQL vs REST in C++: Who Wins? Choosing an API for High Loads

GraphQL vs REST in C++: Choosing an API for High-Load Systems

The debate between REST and GraphQL doesn't subside in any programming language. But when it comes to C++ — a language where every byte and every microsecond counts — the discussion takes on a special tone. Many believe that C++ is only for low-level drivers and game engines, and that web APIs are written in Python, Go, or Rust. However, this is not the case. High-load backends, microservices for financial systems, and IoT platforms where speed is critical are built with C++.

In this article, we'll break down what is better suited for C++ projects: classic REST or modern GraphQL. No fluff — only real C++ code, benchmarks, and practical advice.

REST in C++: A Classic That Works

REST is an architectural style, not a protocol. In C++, it is implemented via HTTP servers. The most popular libraries are CrowCpp, Drogon, and Pistache. They are lightweight, fast, and allow you to quickly set up an API.

Here is what a simple REST endpoint looks like in C++ with CrowCpp:

#include "crow.h"\n\nstruct User {\n    int id;\n    std::string name;\n    std::string email;\n};\n\nint main() {\n    crow::SimpleApp app;\n\n    CROW_ROUTE(app, "/user/<int>")\n    ([](int user_id) {\n        // Emulating a database query\n        User user{user_id, "Alice", "alice@example.com"};\n        \n        crow::json::wvalue x;\n        x["id"] = user.id;\n        x["name"] = user.name;\n        x["email"] = user.email;\n        return x;\n    });\n\n    app.port(8080).multithreaded().run();\n}\n

The advantages of REST in C++ are obvious: minimal overhead, predictable HTTP methods (GET, POST, PUT, DELETE), and a huge number of ready-made tools. You literally write a function, attach a URL to it, and it's done. For simple CRUD operations, REST remains king.

But there are also downsides. In real projects, the problem of over-fetching (retrieving unnecessary data) and under-fetching (needing to make multiple requests) often arises. For example, to get a user and their latest orders, you need two requests: /user/1 and /orders?user_id=1. In C++, this can be solved, but at the cost of writing additional code on the backend.

GraphQL in C++: Flexibility with Typing

GraphQL is a query language that allows the client to request only what is needed. For C++, there are mature libraries: cppgraphqlgen (from Microsoft), taoPQ, and Drogon GraphQL. They generate C++ code from a GraphQL schema, providing strict typing at compile time.

Here is an example of a GraphQL resolver in C++ using cppgraphqlgen:

#include "graphqlservice/GraphQLService.h"\n#include "UserSchema.h" // generated from schema.graphql\n\nclass UserResolver : public graphql::User::Object {\npublic:\n    std::shared_ptr<graphql::User::User> getUser(int32_t id) override {\n        auto user = std::make_shared<graphql::User::User>();\n        user->getId() = id;\n        user->getName() = "Alice";\n        user->getEmail() = "alice@example.com";\n        return user;\n    }\n};\n\nint main() {\n    auto service = std::make_shared<graphql::User::Service>(std::make_shared<UserResolver>());\n    // Starting an HTTP server (e.g., via Crow)\n}\n

The main advantage of GraphQL in C++ is type safety. If you change the schema, the compiler will immediately point out all the places where resolvers need to be fixed. No runtime errors with "unexpected field". For projects with frequent changes to the data model, this saves hours of debugging.

However, flexibility comes at a cost. GraphQL queries are parsed and validated on the server, which adds CPU overhead. In C++, this is not as critical as in Python, but for systems with millions of requests