min read

Key Differences Between REST vs gRPC: Which One to Use? And When?

Explore the comparison between popular APIs and their performance benchmark to know the one suited for you.
Mitul Makadia
Mitul Makadia
Updated on Dec 29/2022
min read
Key Differences Between REST vs gRPC: Which One to Use? And When?
Explore the comparison between popular APIs and their performance benchmark to know the one suited for you.
Mitul Makadia
Updated on Oct 03/2022
Table of contents
What is API?
Monolithic vs Microservices-based Application
What is REST API?
What is RPC API?
What is gRPC API?
Comparison Between gRPC vs REST
What are the Benefits Offered by gRPC?
What are the Downsides of gRPC?
gRPC vs REST – Deeper Comparison
When to Use REST API
When to Use gRPC API
What is the Outcome?
The Difference of a Millisecond
Wrapping Up

What is REST? What is gRPC? Which one fares best in performance in gRPC vs REST? Why use gRPC over REST? What are the differences between gRPC vs REST? What is the performance benchmark when it comes to APIs? Which is faster between gRPC vs REST? Let’s find out answers to these questions and more.

While REST API has been the norm, things are changing up a bit in the tech world. The engineering team at Maruti Techlabs is always looking to improve existing processes. And for the same reason, we decided to do a deep dive into gRPC as the microservices communication framework.

If you’re trying to figure out the gRPC model or consider it an alternative to REST APIs for your project, we have prepared a complete guide to help you understand what gRPC is and how gRPC API compares with the traditional REST API architecture.

What Is Api?

Before comparing gRPC vs REST, let us first understand the basics of APIs(Application programming interfaces). APIs are the set of rules and definitions that enable the applications to interact with each other. API defines the methods and types of calls and requests one application can make to another and formats those data and recommendations.

how api works

APIs support the “pluggability” of applications that create a more extensive system. They allow two applications to communicate even though they are written in different programming languages and running on other platforms.

Monolithic Vs Microservices-based Application

Traditional monolithic applications consist of programming for all services and features within a single unit and an individual code base that manages all benefits of the application. 

Hence, when the developer builds new services and features on top of the existing framework, it becomes difficult to effectively modify and scale the application. Therefore, changing one part of the application can majorly affect the other areas of the application. 

The codebase eventually becomes interdependent and hard to understand after updating, scaling, and changing the application multiple times while working with the traditional system. Later, it becomes necessary to redesign the entire application from scratch, which is practically impossible. 

Microservices-based applications help to overcome this limitation of traditional monolithic applications. The microservices architecture contains breaking of the monolith into its component services and enables them to run as autonomous applications. These components are called microservices which use APIs to interact with each other. 

Because APIs are allowed to run microservices independently, all these microservices have different codes and run on different platforms to interact. Updating individual microservices is faster and more efficient because every independent microservice has less impact on the entire system. 

Unlike monolithic architecture, working with microservice-based architecture is more accessible as it smoothes the scaling of the application by providing the resources to the microservice which requires it. Therefore, if the microservice fails, there are rare chances of the entire system failing.

Read here: How to Configure API Gateway in Microservices Architecture.

Let’s understand ‘what is REST API?’

What Is Rest Api?

REST(Representational State Transfer) API is one of the most popular architectures for building APIs, primarily web-based and microservices-based architecture. REST API enables the support of interoperability between internet-based applications and microservices. 

Using REST API, you can perform the actions like GET, POST, PUT and DELETE on the data entities. Even though REST API uses various formats for receiving and returning messages, JSON is the most commonly used format. JSON is a human-readable format that is efficient, flexible, and platform agnostic. When REST API is available as web services, each service represents a resource to the client.

Therefore, the REST API is the most common architecture for building web applications which generally depends on the HTTP protocol for connecting the microservices. REST built a client-server architecture in which back-end data is available to clients through the JSON or XML format. APIs qualify as “RESTful” when it follows the below constraints:

  • Uniform Interface: Specific application resources should be exposed to the API consumer.
  • Client-Server Independence: Client and server functions perform independently. Therefore, the client will know the URIs directly to the application’s resources, usually published in the API documentation. 
  • Stateless: The server doesn’t save the data about the client request, whereas the client saves this “state data” via a cache. 
  • Cacheable: API should expose the application resources, which must be cacheable
  • Layered: The layered architecture allows the maintenance of different components on other servers. 
  • Code-on-Demand: COD is the only optional REST constraint available. Therefore, it enables the client to receive the code as a response from the server. 

Even though REST is used more widely, REST API is the least commonly used API model to design web applications. The prominent characteristic of this API is that the client has to construct the URLs using the parameters passed out by the server. This is how the browser works- it blindly follows the URLs it finds in the current page received from the server. 

The parsing of the URLs done by the browser extracts the data required to send an HTTP request. Hence, if your API is REST, then your client never has to understand the format of the URLs. Popular API management tools for REST include – Postman, Amazon API Gateway, IBM API Connect, SAP Integration Suite, etc.

What Is Rpc Api?

Unlike REST APIs, RPC(Remote Procedure Call) is a web architecture that allows you to call a function on the remote server in a defined format and receive a response in the same form. RPC architecture doesn’t consider the format of the server executing the request, whether a local server or a remote server. 

However, the primary function of the RPC API is similar to the REST API. The RPC API defines the rules for interaction and methods that enable the interaction process. Later, the client uses the “argument” to call these methods. The arguments that invoke the procedures reside in the query string of URLs. 

For better understanding, below is an example of how an RPC API request compares to a REST API request: 

RPC: RPC API uses POST/deleteResource having the query string that displays {“id”:7}

REST: REST API will write the same request as DELETE/resource/2

Now, let’s understand ‘what is gRPC?’

What Is Grpc Api?

gRPC(Google Remote Procedure Call) is an open-source architecture developed by Google that allows high-speed communication between microservices. It is built upon HTTP/2.0, allowing bi-directional interaction and enabling developers to integrate services programmed in different languages. 

Even though the gRPC consists of HTTP/2.0, HTTP is not exposed to the API designer. gRPC uses the protocol buffers(Protobuf) messaging format, which provides a highly efficient and highly packed messaging format to serialize data. 

Unlike REST, gRPC uses HTTP as a transport layer of the application. Therefore, it allows the developers to define any function calls rather than choose predefined options. 

gRPC stubs and skeletons hide the HTTP from the client and server too. Hence, nobody has to worry about how the RPC maps to HTTP. The client uses a gRPC API by following the below steps:

  • Decide which procedure to call
  • Determine the values of the parameter, if used any
  • Use the code-generated stub to create the call and pass the parameters

The most prominent feature of the gRPC is that when you create a call to a remote system, the sender and receiver receive the local call rather than a remote call executed over the network. This process helps to avoid the coding complexity you would encounter if the application handles a remote call. 

The simplicity of building complex remote calls has made gRPC more popular in the context of APIs in microservices and web applications that entail a vast number of remote calls. GUI tools for gRPC include – omgRPC, gRPCox, Wombat, Milkman.

Comparison Between Grpc Vs Rest

gRPC is one of the many variants of RPC architecture created by Google for effective data transmission between microservices and other systems. gRPC APIs cover the limitations of the REST APIs in the following ways:

Comparison Between gRPC vs REST

1. Using Protobuf instead of JSON/XML

As studied earlier, REST API and RPC APIs commonly transfer the messages using the JSON or XML format. JSON is a flexible, efficient, platform-neutral, language-agnostic, and human-readable language. But the problem with the JSON is that it is not fast enough or lightweight in certain use cases while transmitting data between the systems. 

However, gRPC helps overcome these speed and weight issues using protocol buffers(Protobuf) messaging format. Below are some of the details about Protobuf:

  • Language and platform-agnostic like JSON 
  • Enables the serialization and deserialization of the structured data to communicate with each other via binary
  • Helps to achieve the JSON’s level of human readability by using the highly compressed format
  • It removes many responsibilities that JSON strictly focuses on serializing and deserializing the data by speeding up the data transmission.
  • As Protobuf helps reduce the size of the message, it serves as a lightweight and faster-messaging format for data transmission compared to REST API. 

2. Using HTTP 2 instead of HTTP 1.1

REST APIs are generally built on HTTP 1.1 using a request-response model of communication. That means when microservices receive multiple requests from multiple clients simultaneously, they get served, and hence the entire system slows down. Also, when multiple requests are received parallel, it isn’t easy to return the response to the client in the same order as the requests came in. This problem leads to waiting for the requests sent before they are complete, called head-of-line blocking. REST APIs can also use the HTTP 2 protocol, but it does not utilize HTTP 2 support for streaming and bidirectional communication. 

On the other hand, gRPC uses HTTP 2 to support client-response communication and bidirectional communication. Clients can open the long-lived connections of RPC calls using HTTP 2 stream, also known as multiplexing. 

While working with HTTP 2, microservices receive multiple client requests and achieve multiplexing by simultaneously serving various requests and responses using the data on a single TCP connection. Therefore, gRPC eliminates the limitations of REST APIs by their capacity to stream data constantly.

gRPC enables three types of streaming which are discussed in detail below:

  • Server-side: As the client sends a request message to the server, the server responds to the client. Later, after streaming the response back, the server sends the status message, which suggests completing the process. After this response, the client completes the process. 
  • Client-side: A client sends the request message to the server, and in return, the server shares the response back to the client. Usually, the response is given after receiving the request from the client and a status message. 
  • Bidirectional: The client and server communicate with each other using special orders. Also, the client is the one who initiates and terminates the bidirectional streaming. 

3. Default Code Generation instead of using Third-Party Tools 

While working with REST APIs, you must use third-party tools to auto-generate the code for API calls in various languages. Comparing REST vs gRPC, gRPC supports the inbuilt protoc compiler to support the code generation feature in architecture. 

The protoc compiler in gRPC comes with a wide range of compatibility for various programming languages. Hence, it enables you to connect many different microservices coded in multiple languages and run on various platforms. Therefore, it is wise to use gRPC, which doesn’t depend on the external tool for code generation, unlike REST API, which uses third-party tools like Swagger for API calls. 

4. Fast Message Transmission

According to Ruwan Fernando, gRPC API connections are considerably faster in comparison to REST API connections. The report suggests that “gRPC connections are seven times faster than REST connections for receiving the data and roughly ten times faster for sending the data for specific payload. Fast transmission happens because gRPC is a tight packing of Protobuf and makes wide use of HTTP 2.”

5. Slower Implementation than REST

Even after efficient message transmission speed in gRPC, it is pretty slower to implement than REST API connections. According to Ruan Fernando’s report, it takes about 45 minutes to implement gRPC API services and only 10 minutes to implement REST API. 

The additional time in implementing gRPC suggests the lack of default support for gRPC in third-party tools. Due to this reason, gRPC is not adopted widely compared to the ubiquity of REST APIs. 

6. Ease of Writing Code 

As studied earlier, REST API has very general specifications that you can access anywhere. Therefore, it makes the REST request calls more verbose than they need to be. It is especially true considering the conversion of language-based objects to JSON and vice versa. 

Comparing both gRPC vs REST API, gRPC connection uses less code than REST connection. The REST request also adds much more complexity to the code, which adds 50% of the word count in the code. 

Also, while using REST API, the client is not provided with native language objects, and hence they usually end up creating objects themselves. Unlike REST API, gRPC and protocol buffer provide language native objects to clients and deal with many errors when the compiler catches the API. 

7. Debugging and Support

As JSON objects use the plaintext format, which you can create manually, it becomes easy for the developers to work with REST API. In this condition, if any error occurs, you can manually inspect the JSON objects in your code and figure out the problem. Also, you can add or remove the properties in the JSON objects yourself. Hence, working with REST API is particularly useful when you have never worked with any new API before. 

Since the data in gRPC consists of binary format, it is much harder to directly identify the data passed over the wire using protocol buffers. However, the data transmitted over-represents the native language; you could use pre-existing language and debugging tools to see the objects’ state before responding. 

It is helpful if you can see that data is being passed over the network using JSON objects. But at the same time, robust integration of protocol buffers enables you an easy way to figure out the request call. 

What Are The Benefits Offered By Grpc?

gRPC expresses the benefits of RPC API’s long tradition in an interface description language(IDL) that includes Corba IDL, DCE IDL, and many more. It provides a simple way to define remote procedures compared to REST APIs, which uses URL paths, parameters, and HTTP methods used within them. 

gRPC does not expose any HTTP 2 to the API user or API designer even after using it. It already decides how to layer the RPC model above the HTTP into the gRPC software and default generated code. Therefore, it becomes simpler for API designers and clients to work with the architecture and web services. 

In contrast, OpenAPI requires special designers to specify how the RPC model resides above HTTP for their specific API. However, the OpenAPI approach enables the API client to use the standard HTTP tools and technologies, which for many API designers justifies the efforts. 

You will always develop client-side programming libraries in various languages for programmers regardless of how your API uses HTTP. Later, these programming libraries will take the form of the procedures. Therefore, the most prominent characteristic of gRPC is that it is good at generating client-side programming libraries that are most likely to be used by the programmer and can execute efficiently. 

Similarly, OpenAPI can also generate client-side programming libraries, but while working with gRPC, it is more straightforward and obvious than OpenAPI. It is probably because its IDL only has express RPC concepts and does not involve the simultaneous description of mapping those concepts to HTTP. 

Studies show that gRPC APIs are simple to implement on the server side because of the libraries, frameworks, and code generation that gRPC provides. Compared to writing a standard HTTP request handle that can parse the income request calls of the client and call the appropriate function to implement them, it is easier to create a server implementation of the gRPC method instead. 

Comparing REST vs gRPC, gRPC stands out well in terms of its performance. It uses a binary payload that is efficient enough to build, parse and manage the connections. Although you can use the binary loads and HTTP 2 directly without using gRPC, your client must master more technology to work with it. 

Working with the OpenAPI and REST APIs requires the API providers and clients to figure out how to specify and understand which subset of the HTTP is supported by a particular API. gRPC avoids this problem by allowing the server and the client to adopt the software that helps to implement the complete gRPC protocol. 

What Are The Downsides Of Grpc?

Every technology comes with limitations. The most important feature of HTTP APIs is that the client can use them, and the server implements them using general-purpose and easily available technologies. You can easily make API calls by typing the URL in the browser or firing commands in a bash script or terminal window. Therefore, programmers can easily access or implement the HTTP APIs by using a basic HTTP library. 

In contrast, gRPC requires specific software on both the client and server side. gRPC generated code merged into client and server processes, eventually tricky for those working with dynamic programming like Python and JavaScript. 

Moreover, the Google Cloud Endpoints enable gRPC APIs to be accessed through HTTP and JSON without any special software and restores many options for the clients. But note that not everyone can use the Cloud Endpoints or find or build an equivalent. 

While working with REST API, you can write a bot that crawls the entirety without the metadata, just like a browser or a web bot crawls the entire HTML web page. This procedure cannot be followed while working with RPC-style API because RPC gives each entity type a different API that uses custom software or metadata. 

OpenAPIs and HTTP APIs are often known for adding security features, performing input validation, and solving many other problems. These proxies typically include adding, removing, or parsing the headers and body. These proxies use a combination of custom headers to achieve the desired output, commonly using products like Apigee, which do not require any traditional programming skills or environment that can easily integrate gRPC. It is pretty tricky for gRPC to sort these proxies effectively. 

gRPC does not define a mechanism for preventing data loss when two clients simultaneously try to update the same resource. Also, gRPC is unable to explain the mechanism for making partial updates. Whereas HTTP defines a PATCH method for partial updates, it does not determine what the patch looks like or how to implement it. 

Additional read – Microservices Best Practices To Follow

Grpc Vs Rest – Deeper Comparison

You can use gRPC as a cross-language if you have written a web service in Golang, which makes it very scalable. gRPC uses a protocol buffer for data serialization, making the payloads faster, smaller, and more straightforward. Therefore, gRPC uses an HTTP 2 to support high-scale performance and uses binary data instead of text to make communication more compact and efficient. 

Comparing REST vs gRPC, it is possible to turn off the message compression using the gRPC. You can also send an already compressed image instead of compressing it again, which takes up more time. gRPC is also type-safe. For instance, you cannot consider a banana if it is expecting an apple. Similarly, if the server expects an integer, gRPC won’t allow string because these two are different types.

If we talk about REST API, it is a cross-language that makes web services flexible and scalable. It is the most commonly used web service. Communication in REST often happens using JSON, which is a human-readable language. Therefore, it is easy for developers to determine if the client input is sent correctly to the server and back. 

The most crucial advantage of REST API is that it does not need to set up a client. You just have to make calls to the server address, unlike gRPC, which requires the client setup. 

REST API still holds importance when the payload is small, and several clients simultaneously make a server call. As a result, gRPC is a lot faster than REST API in most cases. When you create a web service that requires many client calls simultaneously and uses small payloads as input and output, REST might be the better choice. 

When To Use Rest Api

If you are building an internal or external system exposed to the rest of the world, REST APIs have been the most preferred app integration choice for a long time. Also, REST API marks its importance when the system needs a high-speed iteration and standardization of HTTP connections. 

Along with the universal support from third-party tools, REST APIs must be your first preference for app integration, microservice integration, and web development services. 

When To Use Grpc Api

Between gRPC vs REST, gRPC APIs are the most commonly used web service to build an internal system closed to external users. With unique features and characteristics, gRPC can be used in some of the following circumstances:

  • Multi-language system: gRPC supports a native code generation system for many development languages and enables you to manage connections within a polyglot environment. 
  • Microservices connections: gRPC supports high-speed throughput communication, allowing you to connect the architectures that consist of lightweight microservices where the message transmission efficiency is paramount. 
  • Low-power/Low-bandwidth networks: As gRPC uses serialized Protobuf messaging system, it offers you a lightweight messaging process along with excellent efficiency, low-power network, and bandwidth-constrained. For instance, IoT is the best example of a network that could benefit from gRPC APIs.
  • Real-time streaming: gRPC enables you to manage bidirectional streaming to send and receive messages in real-time without waiting for Unary client-response communication. 

What Is The Outcome?

Regarding language support, JSON-backed REST API is a clear choice. At the same time, gRPC’s language support has improved drastically over the last few years and is potentially sufficient for most use cases. 

Regarding performance comparisons, if HTTP 1.1 is eliminated from all the use cases, a significant difference is observed between gRPC and REST over HTTP 2. Developers need to write less code to perform the same function in gRPC than REST API. Therefore, gRPC is the correct choice when considering the request performance of the architecture as a key issue.

rest vs grpc

As a result, gRPC is a much better choice while working with internal service-to-service communication. Comparing gRPC vs REST, gRPC has efficient development speed, better performance, and sufficient language neutrality. gRPC impacts on reducing the latency for the customer and provides a better user experience enhancing your product. It lowers the processing time for request calls, which further helps decrease the system’s costs. gRPC improves the performance and efficiency of the developer as a company can afford it at lower prices to develop new features. 

Therefore, we can conclude that building gRPC services is a better choice unless REST is needed to support external clients or language support for which gRPC is not built yet. 

The Difference Of A Millisecond

As studied earlier, the tests show that gRPC is often faster than REST for just a few milliseconds. Now you must think, “Why does this matter?”. Well, a millisecond is a very small unit indeed. Users won’t even realize if their class lasts 1ms longer than usual.

But when discussing a company, 1ms can make a big difference. 

As you know, the server cannot process all the requests simultaneously because it has limited resources available. For instance, a server can process only ten requests simultaneously. In this scenario, the company can only answer ten calls simultaneously because it possesses limited phones or says a limited number of employees to answer the phone. Now, if the server gets 1000 requests and only ten are handled at any moment, the last request would have to wait a long time before it gets dealt with.

Now let us set a benchmark for this scenario. Let’s say you test 10,000 calls to a server that only handles ten requests simultaneously. Here, consider that every gRPC call takes 1ms, and a REST call takes 2ms. That creates a difference of 1 millisecond. At this point, what if your web service makes another request call to another server with the same limited resource before responding?

It will add another second. This adds time when more extensive data is sent to the web service, which eventually makes the difference even more significant in a specific duration. 

A web page could use different web services that get constantly called. All these web services are available with various resources. Hence, when the webpage gets more traffic, it isn’t a matter of milliseconds. After all, the user experience gets affected when the load time of a webpage increases. Many companies solve this issue by purchasing another server.

But you can also fix this problem by analyzing how data transfers from one web service to another.

Wrapping Up

API is an entity-oriented style that standardizes your procedures’ names and imposes other naming conventions. gRPC will enable you to bring some other benefits of its own for your web services. gRPC is especially useful when you use products like cloud endpoints so that your clients are not forced to accept gRPC technologies just because you adopted them. Also, when the API is internal, gRPC plays its prominent role by controlling the technology choices of all your clients and servers. 

REST API is supported widely because every virtual microservices-based architecture entirely depends on the REST APIs as a glue that holds them together. But looking at all the features, characteristics, and advantages that gRPC APIs offer, developers consider it as a “future.” 

APIs in the modern market enable you for faster innovation with evolving technologies. Your company can build better products while standing out from the competition by making correct APIs for your business. In addition to implementing the API architecture to trade, you must ensure that you can handle end-to-end service migrations and development. 

At Maruti Techlabs, we have successfully migrated functional applications from monolithic to microservices architecture. Our DevOps and cloud application development experts factor in the complexity of your application and plan the migration by doing a quick PoC.

Through our services, our clients have achieved more robust applications where the deployment of new features takes less time, traffic routing becomes easier, rollouts happen without downtime, and selective scaling of software components is possible.  

If you too want to modernize your application, simply drop us a note at, and we’ll take it from there.

Mitul Makadia
About the author
Mitul Makadia

Mitul is the Founder and CEO of Maruti Techlabs. From developing business strategies for our clients to building teams and ensuring teamwork at every level, he runs the show quite effortlessly.

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