diff --git a/Gemfile b/Gemfile
index 33017fd..722dc64 100644
--- a/Gemfile
+++ b/Gemfile
@@ -7,6 +7,9 @@ gem 'rails', '~> 5.2.3'
 gem 'pg', '>= 0.18', '< 2.0'
 gem 'puma', '~> 3.11'
 gem 'bootsnap', '>= 1.1.0', require: false
+gem 'activerecord-import'
+gem 'oj'
+gem 'rack-mini-profiler', require: false
 
 group :development, :test do
   # Call 'byebug' anywhere in the code to stop execution and get a debugger console
diff --git a/Gemfile.lock b/Gemfile.lock
index eb22e16..80af6c1 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -33,6 +33,8 @@ GEM
       activemodel (= 5.2.3)
       activesupport (= 5.2.3)
       arel (>= 9.0)
+    activerecord-import (1.0.1)
+      activerecord (>= 3.2)
     activestorage (5.2.3)
       actionpack (= 5.2.3)
       activerecord (= 5.2.3)
@@ -76,9 +78,12 @@ GEM
     nio4r (2.3.1)
     nokogiri (1.10.2)
       mini_portile2 (~> 2.4.0)
+    oj (3.7.12)
     pg (1.1.4)
     puma (3.12.1)
     rack (2.0.6)
+    rack-mini-profiler (1.0.2)
+      rack (>= 1.2.0)
     rack-test (1.1.0)
       rack (>= 1.0, < 3)
     rails (5.2.3)
@@ -134,11 +139,14 @@ PLATFORMS
   ruby
 
 DEPENDENCIES
+  activerecord-import
   bootsnap (>= 1.1.0)
   byebug
   listen (>= 3.0.5, < 3.2)
+  oj
   pg (>= 0.18, < 2.0)
   puma (~> 3.11)
+  rack-mini-profiler
   rails (~> 5.2.3)
   tzinfo-data
   web-console (>= 3.3.0)
diff --git a/app/controllers/trips_controller.rb b/app/controllers/trips_controller.rb
index acb38be..bdd6344 100644
--- a/app/controllers/trips_controller.rb
+++ b/app/controllers/trips_controller.rb
@@ -1,7 +1,7 @@
 class TripsController < ApplicationController
   def index
-    @from = City.find_by_name!(params[:from])
-    @to = City.find_by_name!(params[:to])
-    @trips = Trip.where(from: @from, to: @to).order(:start_time)
+    from = City.find_by_name!(params[:from])
+    to = City.find_by_name!(params[:to])
+    @trips = Trip.includes(bus: :services).where(from: from, to: to).order(:start_time)
   end
 end
diff --git a/app/models/bus.rb b/app/models/bus.rb
index 1dcc54c..ae56e99 100644
--- a/app/models/bus.rb
+++ b/app/models/bus.rb
@@ -13,7 +13,8 @@ class Bus < ApplicationRecord
   ].freeze
 
   has_many :trips
-  has_and_belongs_to_many :services, join_table: :buses_services
+  has_many :bus_services
+  has_many :services, through: :bus_services
 
   validates :number, presence: true, uniqueness: true
   validates :model, inclusion: { in: MODELS }
diff --git a/app/models/bus_service.rb b/app/models/bus_service.rb
new file mode 100644
index 0000000..4e81476
--- /dev/null
+++ b/app/models/bus_service.rb
@@ -0,0 +1,6 @@
+class BusService < ApplicationRecord
+  self.table_name = "buses_services"
+
+  belongs_to :bus
+  belongs_to :service
+end
diff --git a/app/models/service.rb b/app/models/service.rb
index 9cbb2a3..c991963 100644
--- a/app/models/service.rb
+++ b/app/models/service.rb
@@ -12,7 +12,8 @@ class Service < ApplicationRecord
     'Можно не печатать билет',
   ].freeze
 
-  has_and_belongs_to_many :buses, join_table: :buses_services
+  has_many :bus_services
+  has_many :buses, through: :bus_services
 
   validates :name, presence: true
   validates :name, inclusion: { in: SERVICES }
diff --git a/app/models/trip.rb b/app/models/trip.rb
index 9d63dff..f7ba9f6 100644
--- a/app/models/trip.rb
+++ b/app/models/trip.rb
@@ -1,9 +1,9 @@
 class Trip < ApplicationRecord
   HHMM_REGEXP = /([0-1][0-9]|[2][0-3]):[0-5][0-9]/
 
-  belongs_to :from, class_name: 'City'
-  belongs_to :to, class_name: 'City'
-  belongs_to :bus
+  belongs_to :from, class_name: 'City', touch: true
+  belongs_to :to, class_name: 'City', touch: true
+  belongs_to :bus, touch: true
 
   validates :from, presence: true
   validates :to, presence: true
diff --git a/app/services/importer.rb b/app/services/importer.rb
new file mode 100644
index 0000000..611765e
--- /dev/null
+++ b/app/services/importer.rb
@@ -0,0 +1,84 @@
+class Importer
+  attr_reader :json
+
+  def initialize(json)
+    @json = json
+  end
+
+  def call
+    ActiveRecord::Base.transaction do
+      reset_db!
+      import_cities
+      import_services
+      import_busses
+
+      buses = Bus.pluck(:number, :id).to_h
+      cities = City.pluck(:name, :id).to_h
+      link_services(buses)
+      import_trips(buses, cities)
+    end
+  end
+
+  private
+
+  def reset_db!
+    City.delete_all
+    Bus.delete_all
+    Service.delete_all
+    Trip.delete_all
+    BusService.delete_all
+  end
+
+  def import_cities
+    cities = Set.new
+    json.each do |trip|
+      cities << [trip['from']] << [trip['to']]
+    end
+    City.import! [:name], cities.to_a
+  end
+
+  def import_services
+    services = Set.new
+    json.each do |trip|
+      services.merge trip['bus']['services'].map { |el| [el] }
+    end
+    Service.import! [:name], services.to_a
+  end
+
+  def import_busses
+    buses = Set.new
+    json.each do |trip|
+      buses << [trip['bus']['number'], trip['bus']['model']]
+    end
+    Bus.import! [:number, :model], buses.to_a
+  end
+
+  def link_services(buses)
+    services = Service.pluck(:name, :id).to_h
+    joins = Set.new
+    json.each do |trip|
+      bid = buses[trip['bus']['number']]
+      joins.merge(trip['bus']['services'].map { |service| [bid, services[service]] })
+    end
+    BusService.import! [:bus_id, :service_id], joins.to_a
+  end
+
+  def import_trips(buses, cities)
+    trips = Set.new
+    columns = [:from_id, :to_id, :bus_id, :start_time, :duration_minutes, :price_cents]
+    json.each do |trip|
+      from_id = cities[trip['from']]
+      to_id = cities[trip['to']]
+      bus_id = buses[trip['bus']['number']]
+      trips.add [
+        from_id,
+        to_id,
+        bus_id,
+        trip['start_time'],
+        trip['duration_minutes'],
+        trip['price_cents'],
+      ]
+    end
+    Trip.import! columns, trips.to_a
+  end
+end
diff --git a/app/views/trips/_trip.html.erb b/app/views/trips/_trip.html.erb
index fa1de9a..c6342f8 100644
--- a/app/views/trips/_trip.html.erb
+++ b/app/views/trips/_trip.html.erb
@@ -1,5 +1,10 @@
-<li><%= "Отправление: #{trip.start_time}" %></li>
-<li><%= "Прибытие: #{(Time.parse(trip.start_time) + trip.duration_minutes.minutes).strftime('%H:%M')}" %></li>
-<li><%= "В пути: #{trip.duration_minutes / 60}ч. #{trip.duration_minutes % 60}мин." %></li>
-<li><%= "Цена: #{trip.price_cents / 100}р. #{trip.price_cents % 100}коп." %></li>
-<li><%= "Автобус: #{trip.bus.model} №#{trip.bus.number}" %></li>
+<ul>
+  <li><%= "Отправление: #{trip.start_time}" %></li>
+  <li><%= "Прибытие: #{(Time.parse(trip.start_time) + trip.duration_minutes.minutes).strftime('%H:%M')}" %></li>
+  <li><%= "В пути: #{trip.duration_minutes / 60}ч. #{trip.duration_minutes % 60}мин." %></li>
+  <li><%= "Цена: #{trip.price_cents / 100}р. #{trip.price_cents % 100}коп." %></li>
+  <li><%= "Автобус: #{trip.bus.model} №#{trip.bus.number}" %></li>
+    <% if trip.bus.services.any? %>
+      <%= render "services", services: trip.bus.services %>
+    <% end %>
+  </ul>
diff --git a/app/views/trips/index.html.erb b/app/views/trips/index.html.erb
index a60bce4..ed930c3 100644
--- a/app/views/trips/index.html.erb
+++ b/app/views/trips/index.html.erb
@@ -1,16 +1,7 @@
 <h1>
-  <%= "Автобусы #{@from.name} – #{@to.name}" %>
+  <%= "Автобусы #{params[:from]} – #{params[:to]}" %>
 </h1>
 <h2>
-  <%= "В расписании #{@trips.count} рейсов" %>
+  <%= "В расписании #{@trips.size} рейсов" %>
 </h2>
-
-<% @trips.each do |trip| %>
-  <ul>
-    <%= render "trip", trip: trip %>
-    <% if trip.bus.services.present? %>
-      <%= render "services", services: trip.bus.services %>
-    <% end %>
-  </ul>
-  <%= render "delimiter" %>
-<% end %>
+<%= render partial: 'trip', collection: @trips, spacer_template: "delimiter", cached: true %>
diff --git a/case-study.md b/case-study.md
new file mode 100644
index 0000000..a8ba7de
--- /dev/null
+++ b/case-study.md
@@ -0,0 +1,47 @@
+# Case-study оптимизации
+
+## Актуальная проблема
+1. Медленная загрузка данных в базу
+2. Медленная загрузка страницы с расписанием
+
+## Формирование метрики
+Для расчета времени загрузки данных в базу использовался ```Benchmark.realtime```
+Для измерения скорости загрузки страницы использовался ```gem rack-mini-profiler```
+
+## Feedback-Loop
+В качестве референсного файла использовался fixtures/small.json, по результатам обработки которого уже принималось решение относительно эффективности того или иного метода оптимизации.
+Эффективность оптимизаций по скорости загрузки страницы оценивалась на основе метрик ```gem rack-mini-profiler```
+
+### Загрузка данных в базу
+## Находка №1
+Для обработки каждой json записи инициализируется несколько объектов и каждый из них в отдельной транзакции вставляется в базу данных, что крайне неэффективно на больших объемах. Было принято решение использовать ```gem activerecord-import```, для массовой вставки данных
+
+## Находка №2
+Используется устаревший метод ```has_and_belongs_to_many```. Использовав связную модель через ```has many through:```, появляется возможность более эффективно использовать ```gem activerecord import```
+
+## Находка №3
+Используется не самая эффективная библиотека для работы с json. Было принято решение использовать ```gem oj```, для более эффективной обработки
+
+### Загрузка стрaницы
+Замеры проводились после загрузки файла ```fixtures/large.json```
+Исходя из результатов ```gem rack-mini-profiler``` ![miniprofiler-before](images/miniprofiler-before.png) можно сделать следующие выводы:
+
+## Находка №1
+Огромное количество запросов к БД и большое количество N+1 запросов. Принято решение использовать includes для подгрузки ассоциаций и ликвидации лишних запросов.
+
+## Находка №2
+Большое количество времени занимает отрисовка partial. Было принято решение кешировать результаты
+
+## Находка №3
+Проанализировав sql, стало понятно, что не используются индексы на некоторых таблицах
+![table-1](images/table1.png)
+![table-2](images/table2.png)
+Добавив соответствующие индексы удалось существенно ускорить выполнение запросов
+![table-1 after](images/table1-after.png)
+![table-2 after](images/table2-after.png)
+
+## Результаты
+![miniprofiler after](images/miniprofiler-after.png)
+![db load](images/db-load.png)
+
+Благодаря оптимизациям удалось снизить скорость загрузки страницы до 420ms и загрузить требуемый файл за 17сек
diff --git a/config/application.rb b/config/application.rb
index 9c33109..e167ca5 100644
--- a/config/application.rb
+++ b/config/application.rb
@@ -15,5 +15,6 @@ class Application < Rails::Application
     # Application configuration can go into files in config/initializers
     # -- all .rb files in that directory are automatically loaded after loading
     # the framework and any gems in your application.
+    config.autoload_paths += %w(services)
   end
 end
diff --git a/config/initializers/rack_profiler.rb b/config/initializers/rack_profiler.rb
new file mode 100644
index 0000000..96b6cc9
--- /dev/null
+++ b/config/initializers/rack_profiler.rb
@@ -0,0 +1,8 @@
+# frozen_string_literal: true
+
+if Rails.env.development?
+  require "rack-mini-profiler"
+
+  # initialization is skipped so trigger it
+  Rack::MiniProfilerRails.initialize!(Rails.application)
+end
diff --git a/db/migrate/20190503072744_add_index_to_trips.rb b/db/migrate/20190503072744_add_index_to_trips.rb
new file mode 100644
index 0000000..de78ca3
--- /dev/null
+++ b/db/migrate/20190503072744_add_index_to_trips.rb
@@ -0,0 +1,7 @@
+class AddIndexToTrips < ActiveRecord::Migration[5.2]
+  disable_ddl_transaction!
+
+  def change
+    add_index :trips, [:from_id, :to_id], algorithm: :concurrently
+  end
+end
diff --git a/db/migrate/20190503074123_add_index_to_buses_services.rb b/db/migrate/20190503074123_add_index_to_buses_services.rb
new file mode 100644
index 0000000..1b64e3d
--- /dev/null
+++ b/db/migrate/20190503074123_add_index_to_buses_services.rb
@@ -0,0 +1,7 @@
+class AddIndexToBusesServices < ActiveRecord::Migration[5.2]
+  disable_ddl_transaction!
+
+  def change
+    add_index :buses_services, :bus_id, algorithm: :concurrently
+  end
+end
diff --git a/db/schema.rb b/db/schema.rb
index f6921e4..932d998 100644
--- a/db/schema.rb
+++ b/db/schema.rb
@@ -10,9 +10,10 @@
 #
 # It's strongly recommended that you check this file into your version control system.
 
-ActiveRecord::Schema.define(version: 2019_03_30_193044) do
+ActiveRecord::Schema.define(version: 2019_05_03_074123) do
 
   # These are extensions that must be enabled in order to support this database
+  enable_extension "pg_stat_statements"
   enable_extension "plpgsql"
 
   create_table "buses", force: :cascade do |t|
@@ -23,6 +24,7 @@
   create_table "buses_services", force: :cascade do |t|
     t.integer "bus_id"
     t.integer "service_id"
+    t.index ["bus_id"], name: "index_buses_services_on_bus_id"
   end
 
   create_table "cities", force: :cascade do |t|
@@ -40,6 +42,7 @@
     t.integer "duration_minutes"
     t.integer "price_cents"
     t.integer "bus_id"
+    t.index ["from_id", "to_id"], name: "index_trips_on_from_id_and_to_id"
   end
 
 end
diff --git a/images/db-load.png b/images/db-load.png
new file mode 100644
index 0000000..fda5c9e
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diff --git a/images/miniprofiler-after.png b/images/miniprofiler-after.png
new file mode 100644
index 0000000..2e7c6f2
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diff --git a/images/miniprofiler-before.png b/images/miniprofiler-before.png
new file mode 100644
index 0000000..cc5189e
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diff --git a/images/table1-after.png b/images/table1-after.png
new file mode 100644
index 0000000..c9c73c7
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diff --git a/images/table1.png b/images/table1.png
new file mode 100644
index 0000000..2418008
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diff --git a/images/table2-after.png b/images/table2-after.png
new file mode 100644
index 0000000..94e0aac
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diff --git a/images/table2.png b/images/table2.png
new file mode 100644
index 0000000..77ef48e
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diff --git a/lib/tasks/utils.rake b/lib/tasks/utils.rake
index 540fe87..4b837ac 100644
--- a/lib/tasks/utils.rake
+++ b/lib/tasks/utils.rake
@@ -1,34 +1,14 @@
 # Наивная загрузка данных из json-файла в БД
 # rake reload_json[fixtures/small.json]
-task :reload_json, [:file_name] => :environment do |_task, args|
-  json = JSON.parse(File.read(args.file_name))
-
-  ActiveRecord::Base.transaction do
-    City.delete_all
-    Bus.delete_all
-    Service.delete_all
-    Trip.delete_all
-    ActiveRecord::Base.connection.execute('delete from buses_services;')
+require 'benchmark'
+require 'oj'
 
-    json.each do |trip|
-      from = City.find_or_create_by(name: trip['from'])
-      to = City.find_or_create_by(name: trip['to'])
-      services = []
-      trip['bus']['services'].each do |service|
-        s = Service.find_or_create_by(name: service)
-        services << s
-      end
-      bus = Bus.find_or_create_by(number: trip['bus']['number'])
-      bus.update(model: trip['bus']['model'], services: services)
-
-      Trip.create!(
-        from: from,
-        to: to,
-        bus: bus,
-        start_time: trip['start_time'],
-        duration_minutes: trip['duration_minutes'],
-        price_cents: trip['price_cents'],
-      )
-    end
+task :reload_json, [:file_name] => :environment do |_task, args|
+  json = Oj.load(File.read(args.file_name))
+  p 'Start'
+  time = Benchmark.realtime do
+    Importer.new(json).call
   end
+  p 'Done'
+  p time
 end