gRPC vs. REST: Choosing the best API design approach

Modern software development hinges on building applications where clients and servers communicate efficiently. Two standout approaches for building APIs are gRPC and REST. While REST has been the go-to standard for years, gRPC has emerged as serious competition for many use cases.

Let’s compare these technologies in terms of protocol, performance characteristics, and key decision factors to help you make the right choice for your project.

TL;DR: Should I choose gRPC or REST?

We’ll dive deep into both approaches, but if you’re looking for a quick answer:

• Choose REST when simplicity, broad compatibility, and human readability are priorities for your application.
• Go with gRPC when performance, strong typing, and efficient communication are critical.
• Consider a hybrid approach to address various challenges within larger systems.

Now, let’s explore the gRPC vs. REST comparison in detail.

What is REST (Representational State Transfer)?

REST is an architectural style that handles resource manipulation using HTTP methods (GET, POST, PUT, DELETE). It typically encodes data using JSON or XML.

Key characteristics of REST

• Follows standard HTTP methods and status codes
• Stateless communications
• Resource-oriented architecture
• Human-readable payloads (typically JSON)
• Widely accepted across browsers and other platforms

Example REST endpoint

GET /api/users/123 HTTP/1.1
Host: example.com
Accept: application/json

Response

{
  "id": 123,
  "name": "John Smith",
  "email": "[email protected]",
  "created_at": "2025-01-15T08:30:00Z"
}

What is gRPC (gRPC Remote Procedure Call)?

gRPC is Google’s high-performance RPC framework. It uses HTTP/2 as its transport protocol and Protocol Buffers (protobuf) for serialization.

Key characteristics of gRPC

• Built on HTTP/2 (multiplexing, server push, header compression)
• Uses Protocol Buffers for efficient binary serialization
• Strong typing through service definitions
• Bidirectional streaming support
• Code generation for multiple languages

Example gRPC service definition

syntax = "proto3";

service UserService {
  rpc GetUser(GetUserRequest) returns (User) {}
  rpc ListUsers(ListUsersRequest) returns (stream User) {}
  rpc UpdateUser(UpdateUserRequest) returns (User) {}
}

message GetUserRequest {
  int32 user_id = 1;
}

message User {
  int32 id = 1;
  string name = 2;
  string email = 3;
  string created_at = 4;
}

message ListUsersRequest {
  int32 page_size = 1;
  string page_token = 2;
}

message UpdateUserRequest {
  User user = 1;
}

Under the hood: gRPC and HTTP/2

One of gRPC’s most significant technical advantages is its use of HTTP/2 as a transport protocol. Understanding the technical details of HTTP/2 helps explain why gRPC offers substantial performance benefits.

Binary framing layer

HTTP/2 introduces a binary framing layer that fundamentally changes how clients and servers exchange data, unlike HTTP/1.1’s text-based protocol.

• Communication is split into smaller binary-encoded “frames”
• Each frame belongs to a stream (a bidirectional flow of bytes)
• Frames from different streams can be interleaved and later reassembled at the receiving end

Technical advantages for gRPC

• Efficient parsing — Binary protocols parse data faster and with fewer errors than text-based protocols
• Low overhead — Binary encoding reduces the amount of data transmitted over the wire
• Reduced latency — Server processing can begin when the first frame arrives instead of waiting for the entire message

Multiplexing

One of HTTP/2’s biggest features is true multiplexing, which allows multiple request and response messages to travel simultaneously over the same TCP connection.

• Each request/response pair gets a unique stream ID
• All streams connect to a single TCP connection
• Frames from different streams are interleaved and prioritized

Technical advantages for gRPC

• Lower latency with no head-of-line blocking, enabling simultaneous processing of multiple requests
• Connection efficiency by using fewer TCP connections, reducing overhead and resource usage
• Better bandwidth utilization for improved throughput

In REST over HTTP/1.1, browsers create six to eight TCP connections to achieve pseudo-parallelism, which can’t match HTTP/2’s multiplexing optimization.

Header compression with HPACK

HTTP/2 uses HPACK, a specialized compression algorithm designed specifically for HTTP headers. This means it:

• Maintains a dynamic table of previously sent headers
• Encodes header values using Huffman encoding
• Allows headers sent previously to be referenced by index

Technical advantages for gRPC

• Reduced bandwidth usage — Most headers are repetitive between requests, so compressing them saves significant space
• Improved request-response processing speed — Smaller headers are faster to send and process
• More efficient caching — Header compression context is maintained between requests

HPACK can reduce header size by 80-90%, which is especially beneficial for use cases with many small requests or mobile clients operating in limited-bandwidth conditions.

Stream priorities and dependencies

HTTP/2 allows clients to specify dependencies between streams and assign weights to them.

How it works

• Streams can be prioritized relative to one another
• Streams can depend on other streams
• Weights indicate relative importance at the same dependency level

Technical advantages for gRPC

• Optimized resource allocation — Critical resources are delivered first
• Improved user experience — More important API responses can be prioritized
• Better parallel processing control — Dependencies ensure proper ordering when needed

Performance comparison

Serialization and payload size

REST	gRPC
Uses text-based formats (JSON/XML)	Uses binary Protocol Buffers
Larger payload sizes due to text encoding	Typically 30-40% smaller payloads compared to JSON
Human-readable but less efficient	Faster serialization/deserialization
Serialization/deserialization can be CPU-intensive for large payloads	Reduced network bandwidth usage

Network performance

REST	gRPC
Primarily uses HTTP/1.1 (though HTTP/2 is possible)	Built on HTTP/2
One request-response cycle per TCP connection	Multiplexing multiple requests over a single connection
Higher latency with multiple requests	Bidirectional streaming reduces latency
Limited connection reuse	Persistent connections improve performance
Header compression is possible in REST APIs, primarily through the use of HTTP/2’s header compression techniques.	Header compression reduces overhead

Benchmarks

In typical scenarios, gRPC outperforms REST in several metrics:

• Throughput — gRPC handles 5-10 times more requests per second
• Latency — Significantly lower latency, especially with high-frequency communication
• CPU load — More CPU-friendly due to binary serialization
• Network utilization — Reduced bandwidth requirements

Key advantages comparison

REST advantages over gRPC

1. Full browser-level support
   • Native support across all browsers with no extra libraries required
   • Works with HTML forms and JavaScript Fetch API
   • No need for proxy or gateway layers
2. Easy to learn and implement
   • Uses standard HTTP verbs and status codes
   • Doesn’t require special tools to get started
   • JSON is standardized and simple to debug
3. Large and well-established ecosystem and tooling
   • Abundant libraries, frameworks, and middleware
   • Extensive documentation and community resources
   • Well-established security practices
4. Easy to work with
   • Responses can be inspected without specialized tools
   • Simpler debugging and troubleshooting
   • Easy testing through standard tools like curl or Postman
5. Caching Infrastructure
   • Leverages well-established HTTP caching mechanisms
   • Support from CDNs and proxy servers
   • Built-in cache validation through ETag, Last-Modified headers

gRPC Advantages Over REST

1. Performance
   • HTTP/2 multiplexing reduces latency
   • Binary protocol reduces payload size
   • Efficient serialization/deserialization
   • Header compression reduces overhead
2. Strong contract definition
   • Service and message definitions provide clear contracts
   • Type safety across programming languages
   • Built-in schema validation
3. Streaming capabilities
   • Server streaming for data-intensive responses
   • Client streaming for efficient uploads
   • Bidirectional streaming for real-time communication
   • Lower latency for streaming use cases
4. Code generation
   • Automatic client and server code generation
   • Consistent implementations across languages
   • Reduces boilerplate code
   • Type-safe programming experience

When to choose REST

1. Public APIs — When you need broad client compatibility and discoverability
2. Browser-based applications — For direct browser support without gateways
3. Simple CRUD operations — When basic resource operations are sufficient
4. Microservices with diverse language needs — When not all services can support gRPC
5. Human-readable debugging — When payload inspection is important

Example REST-based system:

When to choose gRPC

1. Microservices architecture — When efficient internal service communication is a priority
2. Polyglot environments — For interoperability using consistent code generation
3. Real-time communication — Where gRPC’s streaming capabilities shine
4. Low latency and high throughput systems — Ideal for performance-critical systems
5. IoT and mobile apps — Where bandwidth efficiency and power conservation matter

Example gRPC-based system:

Implementation examples

REST implementation (Node.js/Express):

const express = require('express');
const app = express();
app.use(express.json());

// User data store
const users = {
  123: { id: 123, name: "John Smith", email: "[email protected]", created_at: "2025-01-15T08:30:00Z" }
};

// GET endpoint to fetch a user
app.get('/api/users/:id', (req, res) => {
  const userId = parseInt(req.params.id);
  const user = users[userId];

  if (!user) {
    return res.status(404).json({ error: "User not found" });
  }

  return res.json(user);
});

// POST endpoint to create a user
app.post('/api/users', (req, res) => {
  const newUser = req.body;
  const id = Object.keys(users).length + 1;

  users[id] = {
    id,
    ...newUser,
    created_at: new Date().toISOString()
  };

  return res.status(201).json(users[id]);
});

app.listen(3000, () => {
  console.log('REST API server running on port 3000');
});

gRPC implementation (Node.js):

// user.proto file already defined as shown earlier

const grpc = require('@grpc/grpc-js');
const protoLoader = require('@grpc/proto-loader');

// Load protobuf
const packageDefinition = protoLoader.loadSync('user.proto', {
  keepCase: true,
  longs: String,
  enums: String,
  defaults: true,
  oneofs: true
});

const userProto = grpc.loadPackageDefinition(packageDefinition);

// User data store
const users = {
  123: { id: 123, name: "John Smith", email: "[email protected]", created_at: "2025-01-15T08:30:00Z" }
};

// Implement the service
const server = new grpc.Server();
server.addService(userProto.UserService.service, {
  getUser: (call, callback) => {
    const userId = call.request.user_id;
    const user = users[userId];

    if (!user) {
      return callback({ code: grpc.status.NOT_FOUND, message: 'User not found' });
    }

    callback(null, user);
  },

  listUsers: (call) => {
    // Implement streaming response
    Object.values(users).forEach(user => {
      call.write(user);
    });
    call.end();
  },

  updateUser: (call, callback) => {
    const updatedUser = call.request.user;

    if (!users[updatedUser.id]) {
      return callback({ code: grpc.status.NOT_FOUND, message: 'User not found' });
    }

    users[updatedUser.id] = {
      ...users[updatedUser.id],
      ...updatedUser
    };

    callback(null, users[updatedUser.id]);
  }
});

server.bindAsync('0.0.0.0:50051', grpc.ServerCredentials.createInsecure(), () => {
  console.log('gRPC server running on port 50051');
  server.start();
});

Final verdict: REST or gRPC?

Here are key factors to consider for your project:

1. Client requirements
   • Do you need browser compatibility without gateways?
   • Are mobile clients a primary target?
2. Performance needs
   • Is low latency crucial for your application?
   • Do you need high throughput?
   • Are there bandwidth constraints?
3. Operational considerations
   • • How important is human readability for debugging?
     • Do you need to support legacy systems?

Decision flowchart

Hybrid approaches

A hybrid approach works best for many systems:

1. API gateway pattern
   • External REST API for broad compatibility; internal gRPC communication for performance
   • Gateway handles translation between protocols
2. Progressive migration
   • Start with REST for simplicity
   • Migrate performance-critical paths to gRPC
   • Use both protocols during transition
3. Domain-based selection
   • Use gRPC for data-intensive operations
   • Use REST for simple CRUD operations
   • Select protocol based on specific service needs

Conclusion

Both API patterns have their place in modern software architecture.

REST, with its simplicity and broad compatibility, remains the go-to choice for public APIs and browser-based applications.

gRPC shines in performance-sensitive environments, microservices communication, and cases where strong typing and code generation are essential.

Happy API building!