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Difference between GraphQL and REST API with Example

Hello guys, I have been learning GraphQL since last week and should I say, I am really impressed with its flexibility and how it address some of the pertinent problems with REST APIs. If you don't know, The GraphQL is a query language from Facebook which aims to solves some common problems with REST like a explosion of endpoints, over fetching and under fetching of data, response structure, versioning, and most important performance and Scalability. If you have used REST APIs then you know that you need to send a lot of request to get the data you want. You not only need send multiple request but also you get a lot of unnecessary data which you don't really need, and also need to know multiple endpoints. 

GraphQL aims to solve this problem by providing a single end-point a query language to specify what exactly you need. 

To be honest, I am still far from being a GraphQL expert as I have just started learning GraphQL using Stephen's GraphQL Bootcamp course and some other courses last wee but whatever I have learned so far, shows that GraphQL is here for a long run. 

I have decided to write about my experience with GraphQL so that if someone is also on the same boat they can benefit from it. This is one of the first articles on GraphQL and many more to come. 

Since I have been using REST APIs from a long time with Spring Framework and Spring Boot and my main motivation towards GraphQL is about how does it solve some of the problems with REST, it make sense to start the GraphQL journey by explaining the difference between GraphQL and REST APIs. 




GraphQL vs REST API with Example

There is no better ways to understand the difference between two things but by looking it a practical example and that's what you'll see here. I am using the example from one of my favorite complete guide to building a GraphQL API course by Xavier Decuyper, this is the same example which actually taught me the difference between GraphQL and REST API. 

The example talk about a Blog API, where we have three entities Blogpost, Author and Comments. A Blogpost is written by an Author and it can have one or more comments. If you have to build a REST API to distribute this data then you will start by creating several endpoints for different entities like 

/post/{id} to retrieve a post by id which will return details of a blog post like id, title, content and id of author
/comment/{id} to retrieve a particular comment by id
/author/{id} to retrieve an author by id which will return details of an author like id, name, and its email
/posts to retrieve all posts

Now, this architecture seems fine on theory but if you start using it for practical purpose it will show you the problems REST API faces. For example, if you want to build a feed of blog posts by displaying the title of the all blog posts and name of the author then you need to make several requests to the server. 

Difference between GraphQL and REST API with Example


For example you will need to first send an HTTP request to get all posts using /posts endpoint then you need to get the author name by sending another request to /author/{id} endpoint. 

I agree that its a trivial example but it does pinpoint the problems REST API faces like you need to send a lot of request to get the data you want, which is not only make your application slow because every request to server increases response time but also increase the cost of fetching the data, particularly if you are creating a Mobile app which uses Internet data.

Now, you may argue that why not create another end-point like post_with_authors which can provide all the data you are looking, well that's what many people do but it just mask the problem. It's Ok for this case but what if you need posts with comments details as well, will you create another end-point? If yes, then this will lead to explosion of endpoints which is very hard to maintain, hence not scalable at all. 

Thankfully GraphQL solves all this problem by allowing you to get all the data you need in just one request. With GraphQL, you specify a query which is nothing but the structure of your response. For example, to get the post and author detail you can specify a query like below:

Difference between GraphQL and REST API with Example


When you send this request to GraphQL server it will first fetch the post data and then see the relationship with author, hence fetch the author data in the server and return you exactly what you want. Which means you can get multiple resources in single request without over or under fetching data. 

This is just one example of how GraphQL solves REST API problem and I haven't really gone into details of over fetching of data but if its shows how useful GraphQL can be for APIs. 

Btw, if this example is not clear to you, can you also check out Stephen Griders example in his GraphQL Bootcamp course. Both these courses have helped me to learn GraphQL fundamentals in past week. 




Difference between REST API vs GraphQL

Without wasting anymore of your time, here are some of the important difference between REST API and GraphQL. 

1. Single Endpoint vs Multiple Endpoints
The first and most important difference between GraphQL and REST is that unlike REST which has separate endpoints for getting different set of data, GraphQL provides just one end point to fetch the data you need. 

For example, in the Blogpost API example above, you need to send multiple request to different endpoints to get both post and author data but with GraphQL you got the data by connecting to just one endpoint. 

You may not realize now, but this is a huge advantage in terms of managing and maintaining those end points for a medium to large web application.


2. Data Download (Over fetching and Under fetching)
One of the main problem with REST is that you are either over fetching or under-fetching the data. There is no way for you to download the exact data you want, for example, if you want to download a user's name, age, and city then you just can't download that without downloading the full user object, unless you have a separate endpoint for that. 

Adding a new endpoint may work for one case but you just cannot have endpoints for every single requirement, that would lead to explosion of end-points which would be both difficult to understand and maintain. 

This problem is solved by GraphQL because you specify what exactly you need in form of a Graph query, which means you'll never download too less or too much, instead just right. 


3. Response structure
One of the problem with REST API is that you never 100% sure you what you are getting, I mean you may get more attributes or link to additional endpoints. With GraphQL you know the structure of response well in advance because it exactly matches with the query structure but with REST API, that's not always the case. You may receive an attribute which you even don't know about it. 


4. Relationship
Another important difference between REST and GraphQL is that GraphQL automatically handles relationship for you. For example, if you request for blog post which has comments then GraphQL will also fetch comments details if you have specified that in your query for you. With REST, you need to send another request to fetch data by following the endpoint provided to you.


5. Performance
One of the biggest difference between REST and GraphQL API is the immediate performance gain you get when you switch because of the architecture. If you have understood the Xavier Decuyper example on Complete guide to building a GraphQL API course then you will realize that we have got multiple resources in just one single request, which means a lot of time and bandwidth saving. We also get the exact data we need which means less memory and less parsing headache. 

All these small things adds up and provide much improved performance, particularly in mobile applications where you need to work with limited resources and slow connections. 




Summary

GraphQL is a query language for APIs and a runtime for fulfilling those queries with your existing data. GraphQL provides a complete and understandable description of the data in your API, gives clients the power to ask for exactly what they need and nothing more, makes it easier to evolve APIs over time, and enables powerful developer tools.

Btw, GraphQL also has limitations like, a GPL query always return an HTTP status code of 20o OK, even if the query is not successful, this issue can make error handling difficult. 

Another problem is Caching, GraphQL lacks built-in caching support, so you must provide your own caching support. But, even with these shortcomings, GraphQL still is a better option for APIs. 

If you want to learn more about GraphQL, you can also see these best GraphQL Courses and Tutorials I have been using for my GraphQL learning. 

Difference between GraphQL and REST API with Example


That's all about difference between GraphQL and REST API. It seems a nice alternative of REST API and solves some of the pertaining problems with RESTful web service. I think GraphQL has bright future with Facebook throwing its weight behind. A lot of other companies like Coursera, Github, Yelp have also adopted GraphQL. 


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Thanks for reading this article so far. If you find these GraphQL vs REST API differences and my explanation worth reading then please share them with your friends and colleagues. If you have any questions or feedback, please drop a note.

P. S. - If you are a beginner and want to learn GraphQL in depth and looking for some recommendations then you can also join one of these best GraphQL Courses to start with. This list contains the best course to learn GraphQL from Udemy, Pluralsight and other platforms for beginners.  

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