gRPC vs REST APIs: 3 Critical Differences

Today, the Software Development process relies heavily on APIs (Application Programming Interfaces). An API is a set of codes that allows 2 or more software to communicate with each other. APIs can simplify and speed up the software development process by decreasing its complexity. Moreover, Developers can add functionalities from other software to their existing solutions using APIs. They don’t have to deal with the source code, trying to figure out how the other solution works. They just link their software to another. In other words, APIs act as an abstraction layer between 2 systems, hiding the complexity and details of how they work.

REST (Representational State Transfer) ​​is a type of software architecture that developers use to generate Web APIs. The REST APIs provide simple and uniform interfaces which you can implement to make data, and digital assets available through the web URL. Apart from REST, another popular API design model is gRPC. Google created gRPC as an extension of the RPC (Remote Procedure Call) structure to speed up the data transmission between microservices and other systems. gRPC uses the Protobuf (protocol buffer) to overcome the speed and weight constraints and provides greater efficiency when transmitting messages using its lightweight messaging format. The popularity of these 2 models has given rise to the gRPC vs REST API discussion.

This article will introduce you to REST, RPC, and gRPC models of API development. It will also explain the 3 most popular approaches of building APIs using HTTP. The article will list down the important aspects related to the gRPC vs REST discussion and will explain the use cases of both these models. Read along to learn more about the different models and generate your APIs easily!

Table of Contents

• What is RPC?
• What is REST?
  • How does REST work?
• What is gRPC?
  • How does gRPC work?
• Designing APIs using HTTP
  • gRPC API Model
  • REST API Model
  • OpenAPI Model
• Comparing gRPC vs REST APIs 
  • gRPC vs REST: Working Model
  • gRPC vs REST: Browser Support and Latency
  • gRPC vs REST: Data Formats and Serialization
• gRPC vs REST APIs Use Cases
  • When to use gRPC?
  • When to use REST?
• Conclusion

What is RPC?

The RPC model involves a client-server architecture to generate APIs. The client requests a message that RPC translates and sends to the server. The server responses to the client while the internal message that passes inside the servers are hidden. 

The RPC model like REST establishes rules for client-server interaction. These rules define the “Calls” (requests) and their formats that a client can invoke to call methods that communicate and interact with a service. Moreover, the RPC model allows a client to request a function in a specific format. A benefit of RPC is that it supports remote procedure calls in on-premises and distributed environments. 

To learn more about RPC, visit here.

What is REST?

The REST architectural model follows the HTTP protocol to generate APIs. The REST APIs deliver the backend data response to the clients via JSON or XML messaging format. The advantage of REST API is that you can provide any service that integrates the microservice applications to the client as a resource. The client can access it through one of the following HTTP commands: GET, DELETE, POST, and PUT. 

Nowadays, most developers working on the RCP projects also select a few ideas from HTTP while maintaining the RCP model. Most modern developers map APIs to the same HTTP protocol, regardless of the model used (RPC or REST). 

To learn more about REST, visit here.

How does REST work?

Representational State Transfer (REST), is defined as an architectural style that leverages HTTP as the standard communication protocol for dealing with resources defined in an API. You can think of a resource as an entity similar to an object used in object-oriented programming.

Similar to an object, a RESTful resource has behaviors and properties. Generally, implementations of REST tend to focus more on the properties of a resource with little regard to RESTful behaviors. Implementations that describe a RESTful resource only in terms of properties are considered RESTful.

What is gRPC?

gRPC (Google Remote Procedure Call) is an extension of the RCP architecture. This technology follows the implementation of an RPC API that uses the HTTP 2.0 protocol, however, HTTP is not visible to the API Developer or the Server. So, a high level of abstraction prevents the user from worrying about mapping the RPC concepts to HTTP.

The gRPC model enhances the data transmission speed between microservices. It determines a service, establishes methods and the parameters to allow remote calls and types of return. Moreover, ​It expresses the API RPC model in an Interface Description Language (IDL), which simplifies the task to determine procedures remotely.

To learn more about gRPC, visit here.

How does gRPC work?

The gRPC is meant to allow for fast, efficient communication between a source and target. It is based on the Remote Procedure Call (RPC) architecture, through which a source makes a call to a predefined procedure on the target, usually an endpoint.

Both the messages sent to a procedure and the procedure are defined in a specification file. In gRPC, the specification file utilizes the extension .proto. The following code depicts an example of the specification file animal.proto. The listing defines a method, GetAnimal() as well as two messages Animal and AnimalRequest.

package animalpackage;
syntax = "proto3";
 
service AnimalCatalog {
 // Sends a greeting
 rpc GetAnimal (AnimalRequest) returns (Animal) {}
 }

// defines a request for an animal
message AnimalRequest {
 int32 id = 1;
}

// defines a animal
message Animal {
 int32 id = 1;
 string species = 2;
 string breed = 3;
 int32 legs = 4;
}

Designing APIs using HTTP

Today, most of the APIs implement HTTP as their transmission protocol. So, before moving on to the gRPC vs REST discussion, it is important to understand the models that you can implement to design APIs.

Now, every developer can choose a different model to generate the APIs but all of those models will depend on HTTP in different ways. Using HTTP to build APIs involves the following 3 prominent approaches:

• gRPC API Model
• REST API Model
• OpenAPI Model

1) gRPC API Model

The gRPC model is popular for designing API and uses HTTP with strong abstraction. It implements HTTP / 2 as the basic model protocol but keeps it hidden from the API designer. Furthermore, The Stubs and Skeletons that gRPC generates, enable it to hide HTTP from both client and server. Thus so no one has to worry about how RPC concepts are mapped to HTTP. 

You can use the following 3 steps to use a gRPC API:

•  Step 1: Decide on the procedure that you wish to call. 
•  Step 2: Calculate the required parameter values.
•  Step 3: Use a Stub generated by code to perform the Call and pass the parameter values.

2) REST API Model

Implementing a REST API ensures that your users don’t require to learn the format of your URLs(Uniform Resource Locator). Even the API Specifications given to the user do not include the URL formats. A browser extracts the information needed for an HTTP request and forms an absolute URL using the relative URLs. Moreover, in REST APIs the clients directly use the URLs passed by the server instead of creating new ones.

This implies that in REST APIs the browser does not build the URLs, and it does not understand the website-specific formats of the URLs. The browser blindly follows URLs which it finds on the current page received from the server, tagged by previous pages, or which have been entered by the user.

The REST model although simple is used by only a handful of developers for designing APIs.

3) OpenAPI Model

The gRPC vs REST discussion often eclipses the OpenAPI model which has its own importance. It works in the complete opposite manner as compared to the REST model of API design. A client must have detailed knowledge of the URL formats to use the OpenAPI model. These formats are fundamental to generating requests and constructing URLs. The model supported by OpenAPI is successful and is one of the most intuitive options available to API designers. 

The client model of an OpenAPI and a gRPC API use similar steps. A gRPC client selects a procedure to call and an OpenAPI client decides upon a URL path pattern to use. They both calculate the values ​​of the parameters. A gRPC client uses a Stub procedure and makes the call, an OpenAPI client inputs the parameter values ​​into the URL path pattern and issues an HTTP request. Thus you can conclude that details are different but the basic model structure of Open API and gRPC is very similar.

Comparing gRPC vs REST

Developers often get involved in the gRPC vs REST debate. Now, REST and gRPC are both models using which you can design APIs for your applications. However, deciding which model to use can be a confusing task. The following parameters will help you compare and select the most suitable model for you in the gRPC vs REST discussion:

• gRPC vs REST: Working Model
• gRPC vs REST: Browser Support and Latency
• gRPC vs REST: Data Formats and Serialization

1) gRPC vs REST: Working Model

The gRPC model defines a .proto file which provides a set of rules that both the client and the server must follow for exchanging data. The gRPC compiler has innate code generation capabilities. It is compatible with various programming languages and can integrate various services working on different languages ​​and platforms. Overall, the built-in code generator also makes it easy to create SDKs (Software Development Kits).

REST, on the other hand, works on a set of predefined guidelines to build Web APIs without imposing any regulations. Moreover, the REST API does not offer built-in code generation capabilities. This implies that developers must turn to a third-party tool like Swagger to generate code related to API requests. 

So if you are stuck on the gRPC vs REST question and wish to work on a model with fewer restrictions, try the REST model. You can use the gRPC model if you are seeking in-built code generation features.

2) gRPC vs REST: Browser Support and Latency

Browser support is a major aspect in the gRPC vs REST discussion as most of the Web API communication takes place on the Internet.

The gRPC operates on the HTTP/2 protocol which only a handful of browser supports. Therefore, gRPCweb requires a proxy layer to convert it into  HTTP/2.  The low browser support is the reason that gRPC is limited to internal services only.  Moreover, the HTTP / 2 protocol, applies multiplexed streams. Therefore, multiple clients can send requests in parallel without establishing a new TCP connection for each request. Furthermore, the server can send push notifications to clients through the established connection.

Since the REST model incorporates HTTP 1.1, it receives universal browser support. REST implements HTTP 1.1, which works on a TCP handshaking mechanism for each request. Therefore, REST APIs often suffer from latency issues as the handshake consumes time.

3) gRPC vs REST: Data Formats and Serialization

The gRPC APIs serialize their payload using a Protocol Buffer. This solution allows data compression and thus reduces the message transmission time. Moreover, its Protocol Buffer can easily convert the strongly types messages into client and server understandable programming language.

REST APIs utilize JSON or XML formats to transfer data. JSON provides the flexibility to send dynamic data without worrying about following a rigid structure. Moreover, JSON’s level of human readability is superior to most other data formats. During transmission, the REST API transforms the JSON data to suit the client and server side’s programming language. This hampers the speed of your transmission and makes it error-prone.

This ends the gRPC vs REST discussion. You can decide which model suits you better by considering the above 3 parameters. If you are still having doubts, the next section will help you in identifying the use case of these 2 models so that you can conclude the gRPC vs REST discussion.

gRPC vs REST Use Cases

When to use gRPC?

The third-party tools available today still lack built-in features to support gRPC APIs. As a result, gRPC can only build internal systems and applications that external users can’t access. You can implement the gRPC model in the following use cases:

• Lightweight Microservice connections: gRPC APIs provide the unique combination of low latency and high throughput communication. Thus it is the ideal choice for connecting lightweight microservice architectures where efficient message delivery is essential. 
• Real-time streaming: Real-time communications use gRPC’s ability to handle two-way streaming that enables you to send and receive messages in real-time. 
• Low Power, Low Bandwidth Networks: The gRPC APIs use serialized Protocol Buffer messages to provide lightweight messaging and increased efficiency. These features are suitable for IoT networks that could take advantage of the gRPC APIs.

Apart from this, you can consider gRPC for mobile applications since they do not need a browser and can benefit from smaller messages that can help preserve the mobiles’ processors’ speed.

When to use REST?

REST APIs are the prominent choice for connecting microservice-based applications. They will support your in-house system as well as an open system that shares its resources with the world. The following scenarios are best suited for using REST APIs:

• High-Speed Tasks: REST APIs are the ideal choice when your system requires high-speed iteration of the HTTP protocol. The REST APIs enjoy universal support from third-party tools, thus making it the first choice for application integrations, and web service development.
• Cloud Applications: REST APIs use Stateless Calls and thus, are beneficial in Cloud-based applications. In case of application failure, you can resize and redeploy the Stateless components can seamlessly to accommodate changes in load.  
• Multiple Acess to APIs: REST APIs are not bound to the client-side technology. This allows you to access these APIs from a client-side web project, iOS app, IoT device, or Windows phone. Moreover, you can build your organization’s infrastructure without getting stuck on a particular client-side stack.

The above use cases can be helpful in the gRPC vs REST discussion. Each model has its own advantages and applications. You have to decide which one will fulfill your objective better.

Conclusion

This blog introduced REST, RPC, and gRPC models of API design. It further provided the approaches that you can follow to create your own API using the HTTP protocol. Furthermore, it provided a detailed comparison of the gRPC vs REST discussion. The article also listed down the use cases for both gRPC and REST APIs. In recent decades, REST APIs have dominated the development process, but gRPC is also catching up with it rapidly.

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