REST vs RPC: Comparing Architectural Styles for Web APIs

When designing APIs to handle data communication between frontends, backend servers, and microservices, architects must choose a design style. The two dominant architectural methodologies are REST (Representational State Transfer) and RPC (Remote Procedure Call).

These styles differ in how they model data endpoints: REST is designed around resources and standard HTTP methods, while RPC is designed around executing remote functions.

In this guide, we will compare REST and RPC architectures, analyze URL structures, examine serialization footprints, and establish selection rules.

1. REST: Resource-Oriented Architecture

Representational State Transfer (REST) is a resource-oriented architectural style. It treats data as a set of logical Resources identified by unique URIs.

To manipulate these resources, REST relies exclusively on standard HTTP methods (verbs):

• GET /books: Retrieve the list of books.
• POST /books: Create a new book.
• PUT /books/42: Update book number 42.
• DELETE /books/42: Remove book number 42.

REST uses standard HTTP response status codes (e.g., 200 OK, 201 Created, 404 Not Found) to communicate outcomes.

2. RPC: Procedure-Oriented Architecture

Remote Procedure Call (RPC) is a procedure-oriented (action-oriented) style. It is designed to execute code on a remote server as if it were a local function call.

Instead of defining resources using URLs and utilizing HTTP verbs, RPC maps URLs directly to server Actions. Queries are typically routed through a single entry point (usually using POST requests):

• POST /getBooks: Execute the fetch books function.
• POST /createBook: Execute the create book function.
• POST /updateBook?id=42: Execute the update book function.

Modern Implementations: gRPC and JSON-RPC

While older RPC systems used XML (XML-RPC), modern setups use JSON-RPC or gRPC (developed by Google).

gRPC utilizes Protocol Buffers (Protobuf)—a binary serialization format—running over HTTP/2. This makes gRPC connections extremely fast, highly compressed, and capable of handling bidirectional streaming.

Key Architectural Differences

1. Conceptual Mapping: Resources vs. Actions

• REST maps clean resource nodes. It is highly intuitive for CRUD (Create, Read, Update, Delete) operations on database models.
• RPC maps server actions. It fits scenarios that do not align with basic database rows, such as triggering complex calculations (e.g., /calculateTax), restarting servers, or processing multi-step workflows.

2. Coupling and Contracts

• REST has loose coupling. The client only needs to know the URL paths and response schemas (typically documented via OpenAPI).
• RPC (especially gRPC) requires tight coupling. The client and server must share the exact same .proto interface definition files. If the server updates its interface, the client must update its compiled stub files to prevent compile breaks.

3. Payload and Network Performance

• REST typically transmits plain JSON text over HTTP/1.1. This is human-readable, but has large payload sizes and incurs high head-of-line blocking network latencies.
• gRPC transmits binary Protobuf bytes over HTTP/2. It bypasses text overheads entirely, making it up to 10 times faster than standard REST-JSON APIs.

Feature Summary Comparison

Which Should You Choose?

Choose REST if:

1. You are building public web APIs designed to be consumed by third-party developers, browsers, or mobile applications.
2. Your application is a standard CRUD system manipulating database entities.
3. You want to utilize CDN edge caching to cache read queries.

Choose RPC / gRPC if:

1. You are building an internal microservices cluster where high-speed, low-latency, and multiplexed binary communication is critical.
2. You need to stream real-time data feeds bidirectionally.
3. Your endpoints trigger operations or workflows rather than database row edits.

Conclusion

Both REST and RPC are powerful API design styles. REST is the standard choice for consumer-facing APIs and CRUD web applications, providing human-readable JSON payloads, loose coupling, and native browser cache integrations. RPC (and gRPC) is the ideal engine for high-performance microservices architectures, offering binary compression speeds, strict compile contracts, and advanced streaming capabilities.