This tutorial will guide you about Fast JSON API Serializer. It gives you better performance as compared to Active Model Serializer.

call now for ruby on rails web development

Let’s start with a brief introduction to JSON and Serialization, and how we can use it in Rails application.

What is JSON?

JSON (Javascript Object Notation) is a text-based, human-readable data interchange format used for representing simple data structures and objects in Web browser-based code. It supports:

  • Numbers
  • Strings
  • Arrays or lists
  • Hashes/dictionaries/objects
  • Boolean values
  • Empty values, using null

What is Serialization?

Serialization is the process of turning data structures into another format that can be stored or transmitted over the network.

Examples of serialization formats include JSON, XML, and YAML, so the process of turning any data type into one of these formats is called “serialization.”


  • Declaration syntax similar to Active Model Serializer(AMS)
  • Support for belongs_to, has_many and has_one
  • Support for compound documents (included)
  • Optimized serialization of compound documents
  • Caching

Further Reading: Integrating Google Cloud Vision API with Ruby for Image Object Detection


Let’s create the Rails application.

$ rails new fast_json_api_serializer --database=postgresql

$ cd fast_json_api_serializer

Let’s start with Active Model Serializer and see how much time is required to serializing the data. Then, we will see how we can increase the performance with Fast JSON API.

We are going to use gem ‘active_model_serializers’. Add the following to ‘Gemfile’.

gem 'active_model_serializers'

Run the installer:

$ bundle install

$ rails g scaffold Article title content:text

This command will create the scaffold named ‘Article’ and two columns ‘title’ and ‘content’ to the article model.

$ rails g serializer article title content

This command will create an ‘article’ serializer. It adds ‘article_serializer.rb’ file in ‘app/serializers’ folder. You can see a directory structure as below:

Output 2

Now our ‘article_serializer.rb’ looks like this:

Let’s have a look at ‘articles_controller.rb’ and change the ‘index’ method like below:

Let’s create some sample data. For this, open the ‘seeds.rb’ and add the following code to create the data.

Run the following command:

$ rails db:seed

Start rails server:

$ rails s

Now open the browser and fire the JSON request using localhost:3000/articles.json or you can also use the POSTMAN app.

Let’s see how much time it took for serialization –

Output 3

It took 38.8ms for serialization.

Now we will go with Fast JSON API for better performance.

We are going to use gem ‘fast_jsonapi’. Add the following to ‘Gemfile’.

gem 'fast_jsonapi'

# Note: Don’t remove the gem 'active_model_serializers'.

Run the installer:

$ bundle install

Now change the ‘article_serializer.rb’ as below:

Also, change the ‘index’ method of ‘articles_controller.rb’.

Hit the same URL, http://localhost:3000/articles.json and see response time in terminal:

Output 5

Voila!! Serialization time is fast compared to AMS. It took 5.9ms for serialization.

Compare Responses:

Active Model Serializer:




“content”:”This is article number 1″



{ “data”:

{ “id”:”1″,




“content”:”This is article number 1″



As you see above, Fast JSON API exposes more information compared to Active Model Serializer.

You can find the complete code on Github here.

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