Ruby on Rails for Large-Scale Applications

🚀 Ruby on Rails: Must-Know Principles & Rules for Large-Scale Applications

Building a large-scale Ruby on Rails application requires more than just writing working code. You need clean architecture, maintainability, and scalability to avoid turning your project into a cluttered mess. 🧹

In this guide, we’ll cover essential principles, rules, and bonus tips to keep your Rails app efficient, standardized, and clutter-free. Let’s dive in! 💎

1. Follow the MVC Pattern Properly

Rails is built on Model-View-Controller (MVC), but in large apps, devs often bloat controllers or models. Keep them lean!

❌ Bad Example: Fat Controller

class OrdersController < ApplicationController  
  def create  
    @order = Order.new(order_params)  
    if @order.save  
      UserMailer.order_confirmation(@order).deliver_now  
      PaymentProcessor.charge(@order)  
      redirect_to @order, notice: "Order placed!"  
    else  
      render :new  
    end  
  end  
end  

✅ Good Example: Service Object

# app/services/order_creator.rb  
class OrderCreator  
  def initialize(params)  
    @order = Order.new(params)  
  end  

  def call  
    if @order.save  
      send_confirmation  
      process_payment  
      true  
    else  
      false  
    end  
  end  
end  

# In Controller (Now Lean!)  
def create  
  @order = OrderCreator.new(order_params).call  
  if @order  
    redirect_to @order, notice: "Order placed!"  
  else  
    render :new  
  end  
end  

Why?

• Keeps controllers skinny.
• Business logic is reusable and testable.

2. Use Concerns & Modules for Reusability

Instead of dumping everything in models, extract reusable logic into concerns.

Example: Soft Deletion

# app/models/concerns/soft_deletable.rb  
module SoftDeletable  
  extend ActiveSupport::Concern  

  included do  
    scope :active, -> { where(deleted_at: nil) }  
    scope :deleted, -> { where.not(deleted_at: nil) }  
  end  

  def soft_delete  
    update(deleted_at: Time.current)  
  end  
end  

# In Model  
class User < ApplicationRecord  
  include SoftDeletable  
end  

Why?

• Avoids duplicate code.
• Makes models easier to maintain.

3. Avoid N+1 Queries with Eager Loading

Large apps suffer from slow queries. Always use .includes or .preload.

❌ Bad: N+1 Query

@posts = Post.all  
# In View:  
<% @posts.each do |post| %>  
  <%= post.user.name %> <!-- Queries User for each post! -->  
<% end %>  

✅ Good: Eager Loading

@posts = Post.includes(:user).all  
# Now fetches users in **1 query**!  

Why?

• Boosts performance significantly.

4. Use Background Jobs for Slow Tasks

Never block HTTP requests with long-running tasks (emails, payments, etc.).

Example: Sidekiq Job

# app/jobs/order_confirmation_job.rb  
class OrderConfirmationJob < ApplicationJob  
  def perform(order_id)  
    order = Order.find(order_id)  
    UserMailer.order_confirmation(order).deliver_now  
  end  
end  

# In Controller  
OrderConfirmationJob.perform_later(@order.id)  

Why?

• Keeps response times fast.
• Handles failures gracefully.

5. Keep Configs & Secrets Secure

Never hardcode API keys or env vars. Use dotenv or Rails credentials.

Example: credentials.yml.enc

rails credentials:edit  

stripe:  
  secret_key: YOUR_STRIPE_KEY  

Access in App:

Rails.application.credentials.stripe[:secret_key]  

Why?

• Security best practice.
• Prevents accidental leaks.

6. Write Tests (RSpec/Minitest)

Large apps need tests to avoid regression bugs.

Example: Request Spec

RSpec.describe "Orders", type: :request do  
  it "creates an order" do  
    post orders_path, params: { order: { amount: 100 } }  
    expect(response).to redirect_to(Order.last)  
  end  
end  

Why?

• Catches bugs early.
• Makes refactoring safer.

7. Use Presenters/Decorators for Views

Avoid complex logic in views. Use Draper or plain Ruby objects.

Example: Decorator

# app/decorators/user_decorator.rb  
class UserDecorator  
  def initialize(user)  
    @user = user  
  end  

  def full_name  
    "#{@user.first_name} #{@user.last_name}".titleize  
  end  
end  

# In Controller  
@user = UserDecorator.new(current_user)  

Why?

• Keeps views clean and simple.
• Logic is reusable and testable.

🎁 Bonus Tips for Large Rails Apps

1. Use RuboCop – Enforce consistent code style.
2. Monitor Performance – Use New Relic/Skylight.
3. API Versioning – If building APIs, use /v1/ prefix.
4. Database Indexes – Add them for frequently queried columns.
5. Logging – Use structured logs (JSON) for easier debugging.

Final Thoughts 🎯

Building a large Rails app doesn’t have to be messy. By following these principles, you ensure:
✅ Clean architecture
✅ Better performance
✅ Easier maintenance

Start applying these today, and your future self (and team) will thank you! 🙌

Got more tips? Drop them in the comments! 💬👇

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