gRPC vs. REST: Key Similarities and Differences

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If you’re at all familiar with APIs, you know that REST APIs are the main API used, particularly when it comes to microservices and their applications. gRPC is a high-performance, binary, and strongly-typed protocol using HTTP/2, while REST is a simpler, text-based, and stateless protocol using HTTP with JSON/XML. The main difference is that gRPC is a high-performance, open-source framework designed for efficient communication between services using a binary protocol and HTTP/2, whereas REST is a more established, text-based approach leveraging standard HTTP methods for building web APIs.

Whether you’re trying to figure out what “gRPC” means or you’re considering gRPC as an alternative to REST APIs for your next development project, this guide will help you understand. You’ll learn what gRPC is, why people use it, and how a gRCP API compares to a RESTful API.

Here are some other differences between gRPC and REST:

  • Protocol: gRPC uses HTTP/2 for transport, while REST typically uses HTTP/1.1.
  • Data format: gRPC employs Protocol Buffers for serialization, while REST usually leverages JSON or XML.
  • API design: gRPC is based on the RPC (Remote Procedure Call) paradigm, while REST follows the architectural constraints of the Representational State Transfer model.
  • Streaming: gRPC supports bidirectional streaming, whereas REST is limited to request-response communication patterns.

What Does REST Have Over gRPC? 

Is there a good reason REST is more popular? If you want to understand REST and gRPC, there are a few things you need to know before we dive into the differences.

APIs, or application programming interfaces, provide rules and definitions that allow applications to communicate and interact with each other. An API defines the types of calls and requests one application can make to another, how to make those requests, the data formats to be used, and the conventions clients must follow. 

Essentially, APIs make it possible for applications to be used in larger systems by connecting multiple functions. The functions can work and interact with each other, and you can add more and more functions or microservices.

Microservices may work together even if they were written in different programming languages and running on different platforms. By their very nature, APIs are designed to be compatible. They create the connectivity that is needed between microservices. You can learn more about creating your own APIs with DreamFactory.

Understanding the Architectural Styles in APIs

REST APIs and gRPC APIs refer to different architectural styles for building APIs. While they connect microservices or applications, they have different ways of doing this.

Each architectural style is designed to work in specific cases, so you will need to make a decision based on your needs.

What is a REST API?

REST is the most commonly used architectural style for building APIs. It’s particularly useful for web-based applications and microservices-based infrastructures.

REST APIs use JSON, a text-based, human-readable format that works well with multiple platforms. While not the only format that can be used with REST APIs, it is most commonly used because of its simplicity.

JSON is used to build better links between microservices and internet applications, helping them communicate with each other. These are the most used cases for REST APIs, and you’ll find them everywhere. REST can use JSON to receive and send messages as needed between the microservices.

What is gRPC?

As an open-source RPC architecture,gRPCcreates high-speed communication between microservices. It was originally developed by Google to improve communications.

How do developers use gRPC?This API architecture allows multiple functions created in different programming languages to work together, thanks to the API.  gRPC uses the Protobuf (protocol buffers) messaging format, which is a highly packed, highly efficient messaging format for serializing structured data. For a specific set of use cases, a gRPC API serves as a more efficient alternative to a REST API (more on this later).

Here’s a simple matrix that compares the basics of REST APIs and gRPC:

Characteristic gRPC REST API
HTTP Protocol HTTP 2 HTTP 1.1
Messaging Format Protobuf (Protocol Buffers) JSON (usually) or XML and others
Code Generation Native Protoc Compiler Third-Party Solutions Like Swagger
Communication Unary Client-Request or Bidirectional/Streaming Client-Request Only
Implementation Time 45 Minutes 10 Minutes

APIs in general make it possible to create microservices-based applications, rather than depending only on the slow monolithic applications. It’s necessary to use APIs to create the links between multiple functions so the overall project can work seamlessly. Which API you use will depend on whether it’s a special case or not. 

What Are Microservices-Based Applications?

Microservices-based applications overcome the biggest limitations of traditional, monolithic applications. A monolithic application contains the programming for all of its services and features within a single, indivisible code-base that manages all the services and features of the application. Many companies start out with a monolithic application, as it is often the simplest option.

As developers bolt new services and features on top of the existing framework, it becomes increasingly difficult to modify, upgrade, and scale the application. Changing one part of the app can negatively impact other areas. After scaling, updating, and changing a monolith multiple times, the codebase eventually becomes so interdependent and difficult to understand that it’s necessary to redesign the entire system from scratch. For this reason, more and more companies are working outside the traditional monolithic system. They prefer to use microservices.

A microservices-based application architecture resolves the problem of everything being interconnected. The architectural style breaks a monolith into its component services and runs each component as an autonomous application. The components are referred to as microservices. These individual microservices then use APIs to interact with each other. Together, this API-connected group of microservices forms the larger application architecture. 

Because of the way APIs allow autonomously running microservices to connect with each other, APIs allow you to achieve a pluggable, component-based system. They can work together and communicate even if the microservices are designed and coded in different programming languages or on separate platforms. This makes them extremely useful and also ensures you can use the microservices that work for your needs.

Upgrading individual microservices is dramatically faster and easier because the changes you make to an autonomously running service have less impact on the entire system. Scaling is easier and more efficient, too. Resources can be diverted to the microservices that need them based on usage demands. Moreover, if one microservice fails or slows down, it’s less likely to bring down the entire infrastructure. All of this translates into more efficient, resilient, scalable, and flexible systems, and APIs are what make it possible.

Microservices are used around the world and by major companies, as well as smaller enterprises. You won’t be surprised to learn that Netflix, WordPress, Uber, and Amazon are some companies that use them. With the ability to expand almost infinitely and provide high-quality services and functionality, microservices make sense.

You may have run into situations where you are asked to get an API for use on your website or blog. They can be used to connect small businesses and functions, as well as large ones. They can be scaled as needed.

When starting out, companies need to consider the future. They must consider what applications will be needed in a year or five years. What options may be needed when the business grows? Getting started is literally just the beginning, and it’s shortsighted to begin with a system that will not grow with your company. Instead, it’s best to look at microservices and set everything up from the start with this in mind. The process may take a little longer, but over time, the system will work better for you. It results in less time and money spent over the years too.

The most widely used architectural style for APIs is the REST API. However, there are also RPC APIs and gRPC APIs. In the next sections, we’ll look at how these APIs compare.

Understanding REST APIs

REST (Representational State Transfer) describes a client-server organization in which back-end data is made available to clients through the JSON or XML messaging format. According to Roy Fielding, an API qualifies as “RESTful” when it meets the following constraints:

  • A uniform interface: An API must expose specific application resources to API consumers.
  • Client-server independence: The client and the server function independently. The client will only know the URIs that point to the application’s resources. These are usually published in the API documentation.
  • Stateless: The server doesn’t save any data pertaining to the client request. The client saves this “state data” on its end (via a cache).
  • Cacheable: Application resources exposed by the API need to be cacheable.
  • Layered: The architecture is layered, which allows different components to be maintained on different servers.
  • Code-on-Demand (COD): This is the only optional REST constraint. This allows the client to receive the server's executable code as a response. In other words, the server determines how specific things get done.

It’s also important to note that the REST API uses HTTP protocol in nearly all cases. This is the most common format used with web applications or to interconnect microservices. Once a REST API is publicly available in a web service, clients can use each component as a resource. Usually, the resources are accessible via a common interface that accepts different HTTP commands like GET, POST, DELETE, and PUT.

You may have seen REST APIs in action on sites such as Facebook and Mailchimp. Both these applications use the API architecture differently, but they are still similar. Other sites that use REST include Spotify, Netflix, and Uber.

Creating REST APIs is an excellent way to ensure you get precisely what you want, and our methods make it simple. Avoid some of the issues with developing your own APIs by trying DreamFactory.

Understanding RPC APIs 

RPC or Remote Procedure Call was created first, during the 1970’s and is considered the predecessor of REST. While you can certainly use REST APIs without knowing the history, you may wish to know a bit more about how these older methods worked. RPC causes a function on a remote server, but unlike the newer APIs, it uses a specific format and must receive the same format in response.

The basic concept of an RPC API is similar to that of a REST API. The RPC API defines the interaction rules and methods a client can use to interact with it. Clients submit calls that use “arguments” to invoke these methods. However, the technique is found in the URL with an RPC API. The arguments that invoke the methods are found in the query string. To illustrate this, here’s how an RPC API request compares to a REST API request:

  • RPC: An RPC API request might use POST /deleteResource and have a query string that says { “id”: 3 }  
  • REST: A REST API request would write this request as DELETE /resource/2.

RPC is considered to be somewhat obsolete, and you’ll rarely find it in use these days. In most cases, it has been replaced. The other two options have rapidly overtaken anything that worked with RPC.

How gRPC APIs Work

As a variant of the RPC architecture, gRPC was created by Google in 2015 to speed up data transmission between microservices and other systems that need to interact. This API architecture is somewhat different from previous APIs for several reasons.

First, gRPC uses a different format. Rather than use JSON, the API uses Protobuf. Protobuf was also developed by Google and is language neutral and platform neutral. It’s similar to XML, but considered to be more efficient. 

This API structure also uses HTTP2, instead of the original HTTP1 and is considerably faster than the original RPC. This means it is easier to implement since it can transmit messages up to 10 times faster than previous versions. For larger applications, this makes it possible to manage the communication side of things, though it is slower than REST when implementing the API.

Finally, gRPC uses its own private code generation rather than Swagger for communications. If you want to learn more about all these, read on.

1. Protobuf Instead of JSON/XML

JSON and XML messaging formats are commonly used by both REST APIs and RPC APIs for messaging. While JSON is the most popular choice, thanks to its flexibility and language/platform neutrality, it can be janky and slow when in use.

In contrast to REST and RPC, gRPC overcomes issues related to speed and weight — and offers greater efficiency when sending messages — by using the Protobuf (protocol buffers) messaging format. Here are a few details about Protobuf:

  • Platform and language agnostic like JSON
  • Serializes and deserializes structured data to communicate via binary
  • As a highly compressed format, it doesn’t achieve JSON’s level of human readability
  • Speeds up data transmission by removing many responsibilities JSON manages so it can focus strictly on serializing and deserializing data
  • Data transmission is faster because Protobuf reduces the size of messages and serves as a lightweight messaging format

With Protobuf, some of the downsides associated with gRPC APIs are greatly reduced.

2. Built on HTTP 2 Instead of HTTP 1.1

Another way that gRPC boosts efficiency is through its use of the HTTP 2 protocol. HTTP refers to Hypertext Transfer Protocol and has been in existence since 1989 and is the method of communication throughout the internet.

While REST APIs use HTTP 1.1, gRPC APIs use HTTP 2. There are some notable differences between these two protocols.

HTTP 1.1: Released in 1997, this protocol is commonly considered to be the standard for communication on the World Wide Web. Essentially, it relays information between a computer and a web server, which may be local or remote. The client computer sends a text-based request and a resource is returned. In common use of the WWW, this means an HTML page or a PDF document.

HTTP 2: This protocol was published in 2015 and most modern browsers use it. The fact that Chrome, Internet Explorer, and Safari all make use of HTTP 2 means it is widely adopted. However, it works differently than HTTP 1.1. Rather than maintaining everything in plain text format, HTTP 2 uses binary format encapsulation. This speeds the entire process up and permits more extensive data delivery options.

Simply put, HTTP 2 is faster, more efficient, and reduces network delay through the use of multiplexing.

Using HTTP 2, gRPC offers three types of streaming:

  • Server-side: A client sends a request message to a server. The server returns a stream of responses back to the client. After completing the responses, the server sends a status message (and, in some cases, trailing metadata), which completes the process. After receiving all of the responses, the client completes the process.
  • Client-side: A client sends a stream of request messages to a server. The server returns one response back to the client. It (usually) sends the response after receiving all of the requests from the client and a status message (and sometimes trailing metadata).
  • Bidirectional: A client and server transmit data to one another in no particular order. The client is the one that initiates this kind of bidirectional streaming. The client also ends the connection.

3. In-Born Code Generation Instead of Using Third-Party Tools

At first glance, third-party integration, such as REST APIs use, seems like a good idea. However, it can have some downsides and many prefer the native code generation of gRPC.

gRPC APIs use their own Protoc compiler which allows you to create your own code. It works in multiple languages and can be used in polyglot environments. This refers to groups of microservices that run on separate platforms and are coded in multiple languages.

REST API lacks this native code generation and must use an outside tool. Often, it’s paired with Swagger to ensure multiple languages are created. It’s considered a downside for many, but REST continues to be popular.

4. 7 to 10 Times Faster Message Transmission

According to widely cited tests published by Ruwan Fernando, who has found that gRPC API connections are higher speed than REST API connections. In fact, he reported that they are 7 to 10 times faster: 

“gRPC is roughly 7 times faster than REST when receiving data & roughly 10 times faster than REST when sending data for this specific payload. This is mainly due to the tight packing of the Protocol Buffers and the use of HTTP/2 by gRPC.”

5. Slower Implementation Than REST

Despite the benefits in message transmission speed, this type of API implementation is much slower than REST API implementation. According to Ruan Fernando, it takes approximately 45 minutes to implement a simple gRPC Service. It only takes about 10 minutes to implement a Web or REST API. This is an important factor when choosing the best option for your system.

The delay is due to the fact that there isn’t much support yet for this API structure when it comes to third-party tools. Since gRPC isn’t widely popular yet, it still lacks what it should have in support. Instead of integrating flawlessly and in minutes, the entire process drags out.

Here’s what Fernando says about implementation time: 

“I had to spend roughly 45 mins implementing this simple gRPC Service, where I only spent around 10 mins building the WebAPI. This is mainly due to REST becoming mainstream a long time back, and most major frameworks (i.e., ASP.NET Core MVC) having built-in support to quickly spin up such services (through convention & patterns).”

When Should You Use REST vs. gRPC?

With two options to choose from, which API should you use? That really depends on the project you’re working on and what you need the API to do. REST is still the most common, but that doesn’t mean it should automatically be used.

When Should You Use REST APIs?

When should you use REST APIs? In general, they’re most used for building microservices-based infrastructures. Any time you plan to build an app or a larger computer system that requires connecting microservices, REST is the most common choice.

REST APIs are also best for systems that require speed. If you need standardized HTTP protocol, high-speed iteration, and multi-language microservices connected, then REST should be your main choice. They also have universal support with third-party tools, so are ideal for everything from apps to web services.

When Should You Use gRPC?

As for gRPC, most third-party tools continue to lack in-built features for compatibility. As such, it is mainly relegated to building internal systems, i.e., infrastructures closed to external users. With that caveat in mind, gRPC APIs could be helpful in the following circumstances: 

  • Microservices connections: gRPC’s low-latency and high-speed throughput communication make it particularly useful for connecting architectures that consist of lightweight microservices where the efficiency of message transmission is paramount.
  • Multi-language systems: With its native code generation support for a wide range of development languages, gRPC is excellent when managing connections within a multilingual environment. 
  • Real-time streaming: When real-time communication is a requirement, gRPC’s ability to manage bidirectional streaming allows your system to send and receive messages in real-time without waiting for Unary client-response communication. 
  • Low-power, low-bandwidth networks: gRPC’s use of serialized Protobuf messages offers lightweight messaging, greater efficiency, and speed for bandwidth-constrained, low-power networks (especially when compared to JSON). IoT would be an example of this kind of network that could benefit from this type of API.

You can build your own APIs using a platform for this very purpose. Learn more here.

How to Document Your APIs

Whether you’re using REST APIs or gRPCs, documentation is essential. Even though REST is more popular, it still requires instructions and information. Clients must understand how to use it and be able to configure everything to add to their application. An excellent example of this is when adding functionality to WordPress. Additional microservices can provide every function, from tracking orders to providing multiple language translations and everything in between. Your documentation should be clear enough that any client can use it and get your API set up quickly.

What should be included? The following points are essential for the user to know:

  • What are the relevant endpoints for the API?
  • What terminology is used, and how is it defined?
  • Provide example requests for the endpoints.
  • Information on how to integrate various programming languages.
  • Share the various error messages and status codes for easy reference and troubleshooting.
  • Go step by step, even if it seems overly simplified.

A tutorial on how to use the API and how to add it to a program should be included. Many people prefer to see a video on the steps, but you can also write it out for easy reference. The API documentation should be created by someone who truly knows the system and is able to write clearly, yet simply.

Often, documentation can become dry and technical, so you may need to go over it to ensure everyone is able to use it. This may require using laymen’s terms where needed. You should also consider using numbered steps to make it easier for the client to follow along.

If you are creating the API from scratch with coding on your own, it is often more complicated to create the documentation. You will be fully enveloped in the technical side of things, and it may be difficult to explain to a client. Focus instead on the end user and what they need to know. They don’t need to know how things work, necessarily, just how they can use them.

If you use an outside platform to create your API, you’ll find it is faster and easier to create the documentation to go along with it.

How to Build Your APIs Faster

REST API development is vital to developing a modern, microservices-based application architecture. However, coding a simple REST API can take weeks when you do it by hand — which represents high labor costs and delays for your project. Since it takes so much time, you will want to look at alternatives. For example, certain platforms like DreamFactory iPaaS and API gateway can help.

One of the most useful features of the DreamFactory platform is its capacity to generate REST APIs automatically. With DreamFactory, you generate a fully Swagger-documented REST API to connect virtually any database or service in minutes. 

These platforms are designed to make it simpler and faster to create your APIs. No coding is necessary, and you can do everything you need without learning a single line of code.

Final Thoughts on REST vs. gRPC

Some people consider gRPC as the API of the future. It will be some time before we see a definite lean in that direction, however. As you can see, it isn’t a very popular API choice at this point and it’s doubtful developers will begin to use it extensively in the near future.

REST is universally supported and is already in use everywhere microservices exist. Unless your use case demands gRPC implementation, taking the risk to adopt it at this nascent stage (before widespread adoption) is neither practical nor necessary.

For the moment and probably in the foreseeable future, as well, REST APIs are the best option.

Frequently Asked Questions: gRPC vs REST


Q1: What is gRPC and how does it differ from REST?

gRPC is a high-performance, open-source framework developed by Google, designed for efficient communication between microservices. It uses HTTP/2 for transport and Protocol Buffers for serialization. REST, or Representational State Transfer, is a popular architectural style for building web services, typically using HTTP/1.1 and JSON or XML for data exchange.

Q2: What are the main differences between gRPC and REST?

  • Protocol: gRPC relies on HTTP/2, providing better performance and reduced latency, while REST uses HTTP/1.1.
  • Data format: gRPC employs Protocol Buffers, a binary serialization format, resulting in smaller payloads and faster communication; REST usually leverages JSON or XML, which are text-based formats.
  • API design: gRPC follows the RPC (Remote Procedure Call) paradigm, making it feel like calling local functions; REST adheres to the architectural constraints of the Representational State Transfer model, focusing on resources and state transitions.
  • Streaming: gRPC supports bidirectional streaming, enabling continuous data exchange between client and server; REST is limited to request-response communication patterns.

Q3: When should I use gRPC instead of REST?

Consider using gRPC in scenarios where:

  • High-performance communication and low latency are crucial.
  • You need to support real-time streaming between client and server.
  • You prefer a more function-driven API design.
  • Your system relies heavily on microservices.

Q4: Can gRPC and REST coexist in the same project?

Yes, gRPC and REST can coexist within the same project. You can implement a hybrid approach, using gRPC for specific high-performance microservices and REST for other parts of the system. This allows you to leverage the strengths of both technologies to suit your project's requirements.

Q5: What languages and platforms are supported by gRPC?

gRPC supports a wide range of programming languages, including C++, C#, Dart, Go, Java, Kotlin, Node.js, Objective-C, PHP, Python, Ruby, and Swift. This extensive language support makes it an ideal choice for cross-platform communication and diverse technology stacks.

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