Explain Strategy Pattern and create an example

4- What are some best practices to prevent memory leaks in a Rails application?

class WeeklyEmailJob < ApplicationJob
  queue_as :default

  def perform
    User.find_each do |user|
      UserMailer.weekly_email(user).deliver_now
 end

3- Explain how you would implement a caching strategy for a page that shows the most recent posts to reduce database load.

• 3.1- Explain fragment Caching

  <table>
  <thead>
    <tr>
      <th>Title</th>
      <th>Description</th>
  

2- Indexing Strategy You have a Post model with a large number of records. Explain how you would determine which columns to index and how to implement these indexes.

       create_table :posts do |t|
         t.string :title
         t.integer :user_id
         t.text :text

1- You have a User model with thousands of records. There is an existing query that performs a full table scan, causing significant performance issues. The query looks like this:

users = User.all.select { |user| user.created_at > 1.year.ago && user.active? }

Tasks:

Identify the Problem:

• Explain why this query is causing performance issues.
• Describe what a table scan is and why it’s inefficient in this context.

based on DigitalOcean guide

Create local project

local$ rails new appname -T -d postgresql
local$ rails g scaffold Story title:string body:text
local$ rails db:migrate

install nodejs

sudo apt-get update
curl -sL https://deb.nodesource.com/setup_8.x | sudo -E bash -
curl -sS https://dl.yarnpkg.com/debian/pubkey.gpg | sudo apt-key add -
echo "deb https://dl.yarnpkg.com/debian/ stable main" | sudo tee /etc/apt/sources.list.d/yarn.list
sudo apt-get update
sudo apt-get install git-core curl zlib1g-dev build-essential libssl-dev libreadline-dev libyaml-dev libsqlite3-dev sqlite3 libxml2-dev libxslt1-dev libcurl4-openssl-dev python-software-properties libffi-dev nodejs yarn