diff --git a/.rspec b/.rspec
new file mode 100644
index 00000000..c99d2e73
--- /dev/null
+++ b/.rspec
@@ -0,0 +1 @@
+--require spec_helper
diff --git a/Gemfile b/Gemfile
index e20b1260..5c711958 100644
--- a/Gemfile
+++ b/Gemfile
@@ -8,18 +8,33 @@ gem 'pg', '>= 0.18', '< 2.0'
 gem 'puma', '~> 3.11'
 gem 'bootsnap', '>= 1.1.0', require: false
 
+gem 'pghero'
+# pg_query is used by pghero to provide suggestions to add indexes
+gem 'pg_query', '>= 0.9.0'
+gem 'activerecord-import'
+gem 'rack-mini-profiler'
+gem "strong_migrations"
+# gem 'meta_request'
+# gem 'rails_performance'
+
+
 group :development, :test do
   # Call 'byebug' anywhere in the code to stop execution and get a debugger console
   gem 'byebug', platforms: [:mri, :mingw, :x64_mingw]
+  gem 'rspec-rails', '~> 4.0.0'
 end
 
 group :development do
   # Access an interactive console on exception pages or by calling 'console' anywhere in the code.
   gem 'web-console', '>= 3.3.0'
   gem 'listen', '>= 3.0.5', '< 3.2'
+  gem 'database_cleaner-active_record', '~> 2.0.1'
+  gem 'bullet'
+  gem 'stackprof'
 end
 
 group :test do
+  gem 'rspec-benchmark'
 end
 
 # Windows does not include zoneinfo files, so bundle the tzinfo-data gem
diff --git a/Gemfile.lock b/Gemfile.lock
index fccf6f5f..4f0f1440 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 (1.7.0)
+      activerecord (>= 4.2)
     activestorage (5.2.3)
       actionpack (= 5.2.3)
       activerecord (= 5.2.3)
@@ -43,17 +45,29 @@ GEM
       minitest (~> 5.1)
       tzinfo (~> 1.1)
     arel (9.0.0)
+    benchmark-malloc (0.2.0)
+    benchmark-perf (0.6.0)
+    benchmark-trend (0.4.0)
     bindex (0.6.0)
     bootsnap (1.4.2)
       msgpack (~> 1.0)
     builder (3.2.3)
+    bullet (7.1.6)
+      activesupport (>= 3.0.0)
+      uniform_notifier (~> 1.11)
     byebug (11.0.1)
     concurrent-ruby (1.1.5)
     crass (1.0.4)
+    database_cleaner-active_record (2.0.1)
+      activerecord (>= 5.a)
+      database_cleaner-core (~> 2.0.0)
+    database_cleaner-core (2.0.1)
+    diff-lcs (1.5.1)
     erubi (1.8.0)
     ffi (1.10.0)
     globalid (0.4.2)
       activesupport (>= 4.2.0)
+    google-protobuf (3.23.4)
     i18n (1.6.0)
       concurrent-ruby (~> 1.0)
     listen (3.1.5)
@@ -68,7 +82,9 @@ GEM
     marcel (0.3.3)
       mimemagic (~> 0.3.2)
     method_source (0.9.2)
-    mimemagic (0.3.3)
+    mimemagic (0.3.10)
+      nokogiri (~> 1)
+      rake
     mini_mime (1.0.1)
     mini_portile2 (2.4.0)
     minitest (5.11.3)
@@ -77,8 +93,14 @@ GEM
     nokogiri (1.10.2)
       mini_portile2 (~> 2.4.0)
     pg (1.1.4)
+    pg_query (5.1.0)
+      google-protobuf (>= 3.22.3)
+    pghero (2.8.3)
+      activerecord (>= 5)
     puma (3.12.1)
     rack (2.0.6)
+    rack-mini-profiler (3.1.1)
+      rack (>= 1.2.0)
     rack-test (1.1.0)
       rack (>= 1.0, < 3)
     rails (5.2.3)
@@ -109,6 +131,32 @@ GEM
     rb-fsevent (0.10.3)
     rb-inotify (0.10.0)
       ffi (~> 1.0)
+    rspec (3.13.0)
+      rspec-core (~> 3.13.0)
+      rspec-expectations (~> 3.13.0)
+      rspec-mocks (~> 3.13.0)
+    rspec-benchmark (0.6.0)
+      benchmark-malloc (~> 0.2)
+      benchmark-perf (~> 0.6)
+      benchmark-trend (~> 0.4)
+      rspec (>= 3.0)
+    rspec-core (3.13.0)
+      rspec-support (~> 3.13.0)
+    rspec-expectations (3.13.0)
+      diff-lcs (>= 1.2.0, < 2.0)
+      rspec-support (~> 3.13.0)
+    rspec-mocks (3.13.1)
+      diff-lcs (>= 1.2.0, < 2.0)
+      rspec-support (~> 3.13.0)
+    rspec-rails (4.0.2)
+      actionpack (>= 4.2)
+      activesupport (>= 4.2)
+      railties (>= 4.2)
+      rspec-core (~> 3.10)
+      rspec-expectations (~> 3.10)
+      rspec-mocks (~> 3.10)
+      rspec-support (~> 3.10)
+    rspec-support (3.13.1)
     ruby_dep (1.5.0)
     sprockets (3.7.2)
       concurrent-ruby (~> 1.0)
@@ -117,10 +165,14 @@ GEM
       actionpack (>= 4.0)
       activesupport (>= 4.0)
       sprockets (>= 3.0.0)
+    stackprof (0.2.26)
+    strong_migrations (1.8.0)
+      activerecord (>= 5.2)
     thor (0.20.3)
     thread_safe (0.3.6)
     tzinfo (1.2.5)
       thread_safe (~> 0.1)
+    uniform_notifier (1.16.0)
     web-console (3.7.0)
       actionview (>= 5.0)
       activemodel (>= 5.0)
@@ -134,12 +186,22 @@ PLATFORMS
   ruby
 
 DEPENDENCIES
+  activerecord-import
   bootsnap (>= 1.1.0)
+  bullet
   byebug
+  database_cleaner-active_record (~> 2.0.1)
   listen (>= 3.0.5, < 3.2)
   pg (>= 0.18, < 2.0)
+  pg_query (>= 0.9.0)
+  pghero
   puma (~> 3.11)
+  rack-mini-profiler
   rails (~> 5.2.3)
+  rspec-benchmark
+  rspec-rails (~> 4.0.0)
+  stackprof
+  strong_migrations
   tzinfo-data
   web-console (>= 3.3.0)
 
diff --git a/app/controllers/trips_controller.rb b/app/controllers/trips_controller.rb
index acb38be2..f3afcb1d 100644
--- a/app/controllers/trips_controller.rb
+++ b/app/controllers/trips_controller.rb
@@ -2,6 +2,6 @@ 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)
+    @trips = Trip.where(from: @from, to: @to).includes([bus: [:services]]).order(:start_time)
   end
 end
diff --git a/app/models/buses_service.rb b/app/models/buses_service.rb
new file mode 100644
index 00000000..6219d44e
--- /dev/null
+++ b/app/models/buses_service.rb
@@ -0,0 +1,4 @@
+class BusesService < ApplicationRecord
+  belongs_to :bus
+  belongs_to :service
+end
diff --git a/app/models/trip.rb b/app/models/trip.rb
index 9d63dfff..82920422 100644
--- a/app/models/trip.rb
+++ b/app/models/trip.rb
@@ -17,16 +17,16 @@ class Trip < ApplicationRecord
 
   def to_h
     {
-      from: from.name,
-      to: to.name,
-      start_time: start_time,
-      duration_minutes: duration_minutes,
-      price_cents: price_cents,
-      bus: {
-        number: bus.number,
-        model: bus.model,
-        services: bus.services.map(&:name),
+      'bus' => {
+        'model' => bus.model,
+        'number' => bus.number,        
+        'services' => bus.services.map(&:name),
       },
+      'duration_minutes' => duration_minutes,
+      'from' => from.name,
+      'price_cents' => price_cents,
+      'start_time' => start_time,
+      'to' => to.name
     }
   end
 end
diff --git a/app/services/import_trips_service.rb b/app/services/import_trips_service.rb
new file mode 100644
index 00000000..511f438a
--- /dev/null
+++ b/app/services/import_trips_service.rb
@@ -0,0 +1,49 @@
+class ImportTripsService
+  def self.call(filename)
+    json = JSON.parse(File.read(filename))
+
+    ActiveRecord::Base.transaction do
+      City.delete_all
+      Bus.delete_all
+      Service.delete_all
+      Trip.delete_all
+      ActiveRecord::Base.connection.execute('delete from buses_services;')
+
+      cities = {}
+      services = {}
+      buses = {}
+      buses_services = {}
+
+      trips = []
+
+      json.each do |trip|
+        from = cities[trip['from']] ||= City.new(name: trip['from'])
+        to = cities[trip['to']] ||= City.new(name: trip['to'])          
+
+        bus = buses[trip['bus']['number']] ||= Bus.new(number: trip['bus']['number'], model: trip['bus']['model'])
+
+        trip['bus']['services'].each do |service|
+          bus_service = services[service] ||= Service.new(name: service)
+          buses_services[[bus, bus_service]] ||= BusesService.new(bus: bus, service: bus_service)
+        end          
+
+        trips << Trip.new(
+          from: from,
+          to: to,
+          bus: bus,
+          start_time: trip['start_time'],
+          duration_minutes: trip['duration_minutes'],
+          price_cents: trip['price_cents'],
+        )
+      end
+
+      City.import cities.values
+      Bus.import buses.values
+      Service.import services.values
+      BusesService.import buses_services.values
+      Trip.import trips
+
+      cities, services, buses, trips = nil
+    end   
+  end
+end
\ No newline at end of file
diff --git a/app/views/layouts/application.html.erb b/app/views/layouts/application.html.erb
index e64170ee..bfc813b1 100644
--- a/app/views/layouts/application.html.erb
+++ b/app/views/layouts/application.html.erb
@@ -10,6 +10,8 @@
   </head>
 
   <body>
+    <%= link_to "Database Analyzer", pg_hero_path, target: :blank %>
+    <br><br>
     <%= yield %>
   </body>
 </html>
diff --git a/app/views/trips/_delimiter.html.erb b/app/views/trips/_delimiter.html.erb
deleted file mode 100644
index 3f845ad0..00000000
--- a/app/views/trips/_delimiter.html.erb
+++ /dev/null
@@ -1 +0,0 @@
-====================================================
diff --git a/app/views/trips/_service.html.erb b/app/views/trips/_service.html.erb
deleted file mode 100644
index 178ea8c0..00000000
--- a/app/views/trips/_service.html.erb
+++ /dev/null
@@ -1 +0,0 @@
-<li><%= "#{service.name}" %></li>
diff --git a/app/views/trips/_services.html.erb b/app/views/trips/_services.html.erb
deleted file mode 100644
index 2de639fc..00000000
--- a/app/views/trips/_services.html.erb
+++ /dev/null
@@ -1,6 +0,0 @@
-<li>Сервисы в автобусе:</li>
-<ul>
-  <% services.each do |service| %>
-    <%= render "service", service: service %>
-  <% end %>
-</ul>
diff --git a/app/views/trips/_trip.html.erb b/app/views/trips/_trip.html.erb
deleted file mode 100644
index fa1de9aa..00000000
--- a/app/views/trips/_trip.html.erb
+++ /dev/null
@@ -1,5 +0,0 @@
-<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>
diff --git a/app/views/trips/index.html.erb b/app/views/trips/index.html.erb
index a60bce41..ad5d133a 100644
--- a/app/views/trips/index.html.erb
+++ b/app/views/trips/index.html.erb
@@ -2,15 +2,25 @@
   <%= "Автобусы #{@from.name} – #{@to.name}" %>
 </h1>
 <h2>
-  <%= "В расписании #{@trips.count} рейсов" %>
+  <%= "В расписании #{@trips.length} рейсов" %>
 </h2>
 
 <% @trips.each do |trip| %>
   <ul>
-    <%= render "trip", trip: trip %>
+    <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.present? %>
-      <%= render "services", services: trip.bus.services %>
+      <li>Сервисы в автобусе:</li>
+      <ul>
+        <% trip.bus.services.each do |service| %>
+          <li><%= "#{service.name}" %></li>
+        <% end %>
+      </ul>
     <% end %>
   </ul>
-  <%= render "delimiter" %>
+  ====================================================
 <% end %>
diff --git a/bin/setup b/bin/setup
index f294207b..3fa5f793 100755
--- a/bin/setup
+++ b/bin/setup
@@ -18,7 +18,7 @@ chdir APP_ROOT do
   system('bundle check') || system!('bundle install')
 
   # Install JavaScript dependencies if using Yarn
-  # system('bin/yarn')
+  system('bin/yarn')
 
   # puts "\n== Copying sample files =="
   # unless File.exist?('config/database.yml')
diff --git a/case-study.md b/case-study.md
new file mode 100644
index 00000000..929e04ec
--- /dev/null
+++ b/case-study.md
@@ -0,0 +1,123 @@
+# Case-study оптимизации
+
+## Актуальная проблема: Импорт данных
+К приложению поставляются файлы для импорта рейсов, но скрипт для их загрузки в БД работает очень долго для большого количества рейсов:
+- `small.json` (1K рейсов) - 16,4 сек
+- `medium.json` (10K рейсов) - 131 сек
+- `large.json` (100K рейсов) - **не измерял**, но должны уложиться в бюджет в **пределах минуты**
+
+Будем использовать в качестве метрики загрузку файла с 1К рейсов - **16,4 сек**
+
+### Гарантия корректности работы оптимизированного скрипта
+Перенёс работу скрипта в сервис и написал для него тест:
+```ruby
+context 'Correct trips import' do
+  let(:trip_from_file) { JSON.parse(File.read('fixtures/example.json')) }
+  
+  before { ImportTripsService.call('fixtures/example.json') }
+
+  it 'trips from DB are equal to imported' do
+    expect(Trip.all.map(&:to_h).sort_by(&:to_s)).to eq trip_from_file.sort_by(&:to_s)
+  end    
+end
+```
+Полученные из DB отсортированные рейсы должны быть эквивалентными рейсам из файла. Для проверки немного подкорректировал метод `Trip#to_f`
+
+### Feedback-Loop
+Для эффективной работы по оптимизации выстроил `feedback-loop`, который позволил мне получать обратную связь по эффективности сделанных изменений.
+- Поставил pgHero для изучения поведения запросов
+- В самом скрипте провожу замер скорости выполнения
+- В тесте сервиса слежу, чтобы проводимые изменения не ломали логику выполнения импорта рейсов
+
+
+### Находка №1 - большое количество запросов SELECT
+Изучаем статистику pgHero, обращаем внимание на некоторые нюансы которые видишь впервые:
+- `pkeys` весят соизмеримо с самими талицами
+- При импорте - сами запросы простые, но их количество слишком большое - **12861** запрос на **1000** рейсов
+Сравниваю запросы с кодом скрипта - нахожу строки где вызывается их выполнение. Провожу рефакторинг - в основном добавил хранение City, Service и Bus во временных хэшах.
+- Метрика изменилась: 1К рейсов - с **16,4 сек** до **7,5 сек**. Самих запросов SELECT стало значительно меньше - < 4000
+
+### Находка №2 - добавление индекса к автобусам
+Дальнейшее изучение pgHero показывает, что 44% тратится на INSERT INTO trips и 23% SELECT from buses. Сами рейсы пока трогать не будем, добавим индекс к автобусам. 
+*тогда ещё не был поставлен гем strong_migration, а так он бы поругался, что не хватает concurrency*
+```ruby
+add_index :buses, :number, unique: true
+```
+- SELECT автобусов стал занимать 12%, а общая загрузка уменьшилась до **6,9 сек**
+
+### Находка 3 - activerecord-import
+Становится понятно, что основное время тратится на обращение и подключение к БД при создании объектов, поэтому думаем как это обойти. Для этого будем использовать гем `activerecord-import`, который позволяет сохранить все объекты помещённые во временное хранилище за раз. Добавляем эту возможность в скрипт. Всё работает очень быстро, но тут падает тест на логику импорта - в базе не сохраняются сервисы автобусов. 
+Изучение этой проблемы показало что `activerecord-import` не поддерживает ассоциации (хотя в описании должен). Небольшое ознакомление с проблемой, показало, что не я один сталкивался с ней, но простого решения для неё нет.
+Тогда добавим модель `BusesService` к соединительной таблице `buses_servises`, и собираем и сохраняем объекты тоже отдельно.
+- Метрика изменилась: 1К рейсов - с **6,9 сек** до **1,5 сек**. Ура!
+
+### Попадание в метрику. Выводы. Тесты
+Теперь можно проводить замер и на `large.json` - **55 сек** - как раз укладываемся в метрику!
+Стало интересно сколько тратится памяти при таком импорте данных:
+- small  - 1.5 sec - 113 MB
+- medium - 7 sec   - 181 MB
+- large  - 55 sec  - 732 MB
+
+Думал, что с увеличением количества рейсов памяти будет расходоваться больше. Наверное, из-за того что данные повторяются не происходит большой расход памяти.
+Можно было попробовать обновить версию `rails` до 6 и использовать `insert_all`, или переписать импорт на потоковый режим, чтобы попытаться осилить файлы побольше, но так как имеется отставание по времени прохождения курса - переходим ко второй части ДЗ.
+- Защитил скрипт тестом, время импорта 1000 рейсов не должно быть больше 2-х сек
+```ruby
+expect { ImportTripsService.call('fixtures/small.json') }.to perform_under(2).sec
+```
+
+## Актуальная проблема: Отображение расписаний
+Когда рейсов становится слишком много страница с расписанием грузится очень медленно.
+С файлом `small` время страницы `http://localhost:3000/автобусы/Самара/Москва` - 579ms
+
+### Находка 1 - чрезмерная загрузка паршиалов + COUNT
+Первым делом изучаем логи сервера:
+```log
+Completed 200 OK in 579ms (Views: 475.8ms | ActiveRecord: 81.6ms)
+```
+Большая часть времени - загрузка вьюх. И много времени уходит на запрос COUNT (@trips.count). Помним, что это всегда лишний запрос, поэтому меняем на #size. Эффекта нет - запрос COUNT продолжает отправляться. Пробуем #length - помогает. *Интересно, как в современных рельсах работает вопрос о размере*
+Рефакторим вьюхи и меняем count на length:
+```log
+Completed 200 OK in 180ms (Views: 107.2ms | ActiveRecord: 70.1ms)
+```
+Наблюдаем положительный эффект и там и там
+
+### Находка 2 Eager loading
+Так как тема текущего урока - оптимизация БД, а не вьюх - увеличиваем количество рейсов до 10000 (medium.json). Время загрузки - 800 мс
+Ставим `bullet` - он советует добавить:
+- includes([:bus])
+- includes([:services])
+Получаем время загрузки вместо **800 мс - 155 мс**. Помним о `preload` - ставим его вместо `includes`, но разницы по времени вообще не получаем, поэтому оставляем `includes` - как и советовал изначально `bullet`
+
+### Находка 3 - индексы
+Увеличиваем кол-во рейсов до 100к. Наш запрос занимает 600 мс. Из них 530 - вьюха, 48 - AR
+Уже до этого ставили `rack-mini-profiler`, но знакомился с ним поверхностно - обращал внимание только на общее время загрузки страницы. Теперь решил изучить подробнее. Большое положительное удивление доставило количество опций - когда можно открывать отчёт с другими профилировщиками. Когда видишь это на уроке - не проникаешься его мощью. Но когда уже все запросы как родные - `rack-mini-profiler` может заменить почти всё остальное (наверное)
+
+Изучение `pgHero` и `rack-mini-profiler` показывает, что **41%** времени занимает занимает запрос рейсов где идёт поис `from_id` -> `to_id` - Значит, это первый претендент на индекс.
+
+Перед добавлением индексов ставим:
+- strong_migrations
+- rails panel
+- rails_performance (вообще ничего интересного не показал)
+
+Добавляем индекс к
+- cities :names
+- trips [:from_id, :to_id]
+`strong_migrations` предлагает использовать опции `disable_ddl_transaction!`, `algorithm: :concurrently` - окей, мы для этого его и ставили.
+Получаем загрузку ActiveRecord: 18 ms. Загрузка вьюх остаётя прежней. 
+
+Считаю, оптимизации загрузки страниц с рейсами мы добились.
+
+### Попадание в метрику. Выводы. Тесты
+Итак страница с 1004 рейсами из 100_000 грузится за 485ms, из которых работа с БД - 20 ms. Возможно можно добавить пагинацию, или соорудить один мощный запрос, но уже поджимает время сдачи. Считаю что попадаем в метрику загрузки страницы с рейсами.
+
+Пишем тест для защиты полученных результатов в оптимизации. Он заключается в том, что экшен trips#index с параметрами Самара -> Москва должен отработать менее чем за 5 мс (100 000 записей в БД)
+```ruby
+  describe 'GET #index' do
+    before { ImportTripsService.call('fixtures/medium.json') }
+
+    it 'load 10 000 trips under 5 ms' do
+      expect { get :index, params: { from: 'Самара', to: 'Москва' } }.to perform_under(5).ms
+    end
+  end
+  ```
+
diff --git a/config/database.yml b/config/database.yml
index e116cfa6..451421c4 100644
--- a/config/database.yml
+++ b/config/database.yml
@@ -20,6 +20,8 @@ default: &default
   # For details on connection pooling, see Rails configuration guide
   # http://guides.rubyonrails.org/configuring.html#database-pooling
   pool: <%= ENV.fetch("RAILS_MAX_THREADS") { 5 } %>
+  host: localhost
+  port: 5432
 
 development:
   <<: *default
@@ -29,19 +31,19 @@ development:
   # To create additional roles in postgres see `$ createuser --help`.
   # When left blank, postgres will use the default role. This is
   # the same name as the operating system user that initialized the database.
-  #username: task-4
+  username: bb_db_user
 
   # The password associated with the postgres role (username).
-  #password:
+  password: 340242
 
   # Connect on a TCP socket. Omitted by default since the client uses a
   # domain socket that doesn't need configuration. Windows does not have
   # domain sockets, so uncomment these lines.
-  #host: localhost
+  # host: localhost
 
   # The TCP port the server listens on. Defaults to 5432.
   # If your server runs on a different port number, change accordingly.
-  #port: 5432
+  # port: 5432
 
   # Schema search path. The server defaults to $user,public
   #schema_search_path: myapp,sharedapp,public
@@ -58,6 +60,8 @@ development:
 test:
   <<: *default
   database: task-4_test
+  username: bb_db_user
+  password: 340242
 
 # As with config/secrets.yml, you never want to store sensitive information,
 # like your database password, in your source code. If your source code is
diff --git a/config/environments/development.rb b/config/environments/development.rb
index 1311e3e4..8468e80a 100644
--- a/config/environments/development.rb
+++ b/config/environments/development.rb
@@ -1,4 +1,13 @@
 Rails.application.configure do
+  # config.after_initialize do
+  #   Bullet.enable        = true
+  #   Bullet.alert         = true
+  #   Bullet.bullet_logger = true
+  #   Bullet.console       = true
+  #   Bullet.rails_logger  = true
+  #   Bullet.add_footer    = true
+  # end
+
   # Settings specified here will take precedence over those in config/application.rb.
 
   # In the development environment your application's code is reloaded on
diff --git a/config/initializers/strong_migrations.rb b/config/initializers/strong_migrations.rb
new file mode 100644
index 00000000..a79084a4
--- /dev/null
+++ b/config/initializers/strong_migrations.rb
@@ -0,0 +1,26 @@
+# Mark existing migrations as safe
+StrongMigrations.start_after = 20240521214041
+
+# Set timeouts for migrations
+# If you use PgBouncer in transaction mode, delete these lines and set timeouts on the database user
+StrongMigrations.lock_timeout = 10.seconds
+StrongMigrations.statement_timeout = 1.hour
+
+# Analyze tables after indexes are added
+# Outdated statistics can sometimes hurt performance
+StrongMigrations.auto_analyze = true
+
+# Set the version of the production database
+# so the right checks are run in development
+# StrongMigrations.target_version = 10
+
+# Add custom checks
+# StrongMigrations.add_check do |method, args|
+#   if method == :add_index && args[0].to_s == "users"
+#     stop! "No more indexes on the users table"
+#   end
+# end
+
+# Make some operations safe by default
+# See https://github.com/ankane/strong_migrations#safe-by-default
+# StrongMigrations.safe_by_default = true
diff --git a/config/routes.rb b/config/routes.rb
index a2da6a7b..c606f2b9 100644
--- a/config/routes.rb
+++ b/config/routes.rb
@@ -2,4 +2,6 @@
   # For details on the DSL available within this file, see http://guides.rubyonrails.org/routing.html
   get "/" => "statistics#index"
   get "автобусы/:from/:to" => "trips#index"
+
+  mount PgHero::Engine, at: "pgdashboard"
 end
diff --git a/db/migrate/20240520181028_add_index_to_buses_number.rb b/db/migrate/20240520181028_add_index_to_buses_number.rb
new file mode 100644
index 00000000..b1e57d2b
--- /dev/null
+++ b/db/migrate/20240520181028_add_index_to_buses_number.rb
@@ -0,0 +1,5 @@
+class AddIndexToBusesNumber < ActiveRecord::Migration[5.2]
+  def change
+    add_index :buses, :number, unique: true
+  end
+end
diff --git a/db/migrate/20240521220915_add_index_to_trips_from_id_and_to_id.rb b/db/migrate/20240521220915_add_index_to_trips_from_id_and_to_id.rb
new file mode 100644
index 00000000..0e5f6898
--- /dev/null
+++ b/db/migrate/20240521220915_add_index_to_trips_from_id_and_to_id.rb
@@ -0,0 +1,7 @@
+class AddIndexToTripsFromIdAndToId < ActiveRecord::Migration[5.2]
+  disable_ddl_transaction!
+
+  def change
+    add_index :trips, [:from_id, :to_id], unique: false, algorithm: :concurrently
+  end
+end
diff --git a/db/migrate/20240521221903_add_index_to_cities_name.rb b/db/migrate/20240521221903_add_index_to_cities_name.rb
new file mode 100644
index 00000000..0138da52
--- /dev/null
+++ b/db/migrate/20240521221903_add_index_to_cities_name.rb
@@ -0,0 +1,7 @@
+class AddIndexToCitiesName < ActiveRecord::Migration[5.2]
+  disable_ddl_transaction!
+
+  def change
+    add_index :cities, :name, algorithm: :concurrently
+  end
+end
diff --git a/db/migrate/20240521222235_add_index_to_buses_services_bus.rb b/db/migrate/20240521222235_add_index_to_buses_services_bus.rb
new file mode 100644
index 00000000..d808482d
--- /dev/null
+++ b/db/migrate/20240521222235_add_index_to_buses_services_bus.rb
@@ -0,0 +1,7 @@
+class AddIndexToBusesServicesBus < 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 f6921e45..a5028685 100644
--- a/db/schema.rb
+++ b/db/schema.rb
@@ -10,23 +10,27 @@
 #
 # 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: 2024_05_21_222235) 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|
     t.string "number"
     t.string "model"
+    t.index ["number"], name: "index_buses_on_number", unique: true
   end
 
   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|
     t.string "name"
+    t.index ["name"], name: "index_cities_on_name"
   end
 
   create_table "services", force: :cascade do |t|
@@ -40,6 +44,7 @@
     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/lib/tasks/simple_task.rake b/lib/tasks/simple_task.rake
new file mode 100644
index 00000000..3c11793e
--- /dev/null
+++ b/lib/tasks/simple_task.rake
@@ -0,0 +1,56 @@
+  # rake demo:reload_json[fixtures/small.json]
+namespace :demo do
+  task :reload_json, [:file_name] => :environment do |_task, args|
+
+    time = Benchmark.measure do
+      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;')
+
+        cities = {}
+        services = {}
+        buses = {}
+        buses_services = {}
+
+        trips = []
+
+        json.each do |trip|
+          from = cities[trip['from']] ||= City.new(name: trip['from'])
+          to = cities[trip['to']] ||= City.new(name: trip['to'])          
+
+          bus = buses[trip['bus']['number']] ||= Bus.new(number: trip['bus']['number'], model: trip['bus']['model'])
+
+          trip['bus']['services'].each do |service|
+            bus_service = services[service] ||= Service.new(name: service)
+            buses_services[[bus, bus_service]] ||= BusesService.new(bus: bus, service: bus_service)
+          end          
+
+          trips << Trip.new(
+            from: from,
+            to: to,
+            bus: bus,
+            start_time: trip['start_time'],
+            duration_minutes: trip['duration_minutes'],
+            price_cents: trip['price_cents'],
+          )
+        end
+
+        City.import cities.values
+        Bus.import buses.values
+        Service.import services.values
+        BusesService.import buses_services.values
+        Trip.import trips
+
+        cities, services, buses, trips = nil
+      end      
+    end
+
+    puts "Done in #{time.real} seconds"
+    puts "MEMORY USAGE: %d MB" % (`ps -o rss= -p #{Process.pid}`.to_i / 1024)
+  end
+end
diff --git a/lib/tasks/utils.rake b/lib/tasks/utils.rake
index 540fe871..fc13eebc 100644
--- a/lib/tasks/utils.rake
+++ b/lib/tasks/utils.rake
@@ -1,34 +1,54 @@
-# 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;')
-
-    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
+
+  time = Benchmark.measure do
+    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;')
+
+      cities = {}
+      services = {}
+      buses = {}
+      buses_services = {}
+
+      trips = []
+
+      json.each do |trip|
+        from = cities[trip['from']] ||= City.new(name: trip['from'])
+        to = cities[trip['to']] ||= City.new(name: trip['to'])          
+
+        bus = buses[trip['bus']['number']] ||= Bus.new(number: trip['bus']['number'], model: trip['bus']['model'])
+
+        trip['bus']['services'].each do |service|
+          bus_service = services[service] ||= Service.new(name: service)
+          buses_services[[bus, bus_service]] ||= BusesService.new(bus: bus, service: bus_service)
+        end          
+
+        trips << Trip.new(
+          from: from,
+          to: to,
+          bus: bus,
+          start_time: trip['start_time'],
+          duration_minutes: trip['duration_minutes'],
+          price_cents: trip['price_cents'],
+        )
       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
+
+      City.import cities.values
+      Bus.import buses.values
+      Service.import services.values
+      BusesService.import buses_services.values
+      Trip.import trips
+
+      cities, services, buses, trips = nil
+    end      
   end
+
+  puts "Done in #{time.real} seconds"
+  puts "MEMORY USAGE: %d MB" % (`ps -o rss= -p #{Process.pid}`.to_i / 1024)
 end
diff --git a/spec/controllers/trips_controller_spec.rb b/spec/controllers/trips_controller_spec.rb
new file mode 100644
index 00000000..e4f8708d
--- /dev/null
+++ b/spec/controllers/trips_controller_spec.rb
@@ -0,0 +1,12 @@
+require 'rails_helper'
+
+RSpec.describe TripsController, type: :controller do
+
+  describe 'GET #index' do
+    before { ImportTripsService.call('fixtures/medium.json') }
+
+    it 'load 10 000 trips under 5 ms' do
+      expect { get :index, params: { from: 'Самара', to: 'Москва' } }.to perform_under(5).ms
+    end
+  end
+end
diff --git a/spec/rails_helper.rb b/spec/rails_helper.rb
new file mode 100644
index 00000000..00345af7
--- /dev/null
+++ b/spec/rails_helper.rb
@@ -0,0 +1,64 @@
+# This file is copied to spec/ when you run 'rails generate rspec:install'
+require 'spec_helper'
+ENV['RAILS_ENV'] ||= 'test'
+require File.expand_path('../config/environment', __dir__)
+# Prevent database truncation if the environment is production
+abort("The Rails environment is running in production mode!") if Rails.env.production?
+require 'rspec/rails'
+# Add additional requires below this line. Rails is not loaded until this point!
+
+# Requires supporting ruby files with custom matchers and macros, etc, in
+# spec/support/ and its subdirectories. Files matching `spec/**/*_spec.rb` are
+# run as spec files by default. This means that files in spec/support that end
+# in _spec.rb will both be required and run as specs, causing the specs to be
+# run twice. It is recommended that you do not name files matching this glob to
+# end with _spec.rb. You can configure this pattern with the --pattern
+# option on the command line or in ~/.rspec, .rspec or `.rspec-local`.
+#
+# The following line is provided for convenience purposes. It has the downside
+# of increasing the boot-up time by auto-requiring all files in the support
+# directory. Alternatively, in the individual `*_spec.rb` files, manually
+# require only the support files necessary.
+#
+# Dir[Rails.root.join('spec', 'support', '**', '*.rb')].sort.each { |f| require f }
+
+# Checks for pending migrations and applies them before tests are run.
+# If you are not using ActiveRecord, you can remove these lines.
+begin
+  ActiveRecord::Migration.maintain_test_schema!
+rescue ActiveRecord::PendingMigrationError => e
+  puts e.to_s.strip
+  exit 1
+end
+RSpec.configure do |config|
+  # Remove this line if you're not using ActiveRecord or ActiveRecord fixtures
+  config.fixture_path = "#{::Rails.root}/spec/fixtures"
+
+  # If you're not using ActiveRecord, or you'd prefer not to run each of your
+  # examples within a transaction, remove the following line or assign false
+  # instead of true.
+  config.use_transactional_fixtures = true
+
+  # You can uncomment this line to turn off ActiveRecord support entirely.
+  # config.use_active_record = false
+
+  # RSpec Rails can automatically mix in different behaviours to your tests
+  # based on their file location, for example enabling you to call `get` and
+  # `post` in specs under `spec/controllers`.
+  #
+  # You can disable this behaviour by removing the line below, and instead
+  # explicitly tag your specs with their type, e.g.:
+  #
+  #     RSpec.describe UsersController, type: :controller do
+  #       # ...
+  #     end
+  #
+  # The different available types are documented in the features, such as in
+  # https://relishapp.com/rspec/rspec-rails/docs
+  config.infer_spec_type_from_file_location!
+
+  # Filter lines from Rails gems in backtraces.
+  config.filter_rails_from_backtrace!
+  # arbitrary gems may also be filtered via:
+  # config.filter_gems_from_backtrace("gem name")
+end
diff --git a/spec/services/import_trips_service_spec.rb b/spec/services/import_trips_service_spec.rb
new file mode 100644
index 00000000..945b4d72
--- /dev/null
+++ b/spec/services/import_trips_service_spec.rb
@@ -0,0 +1,21 @@
+require 'rails_helper'
+
+describe "ImportTripsService" do
+  context 'Correct trips import' do
+    let(:trip_from_file) { JSON.parse(File.read('fixtures/example.json')) }
+    
+    before { ImportTripsService.call('fixtures/example.json') }
+
+    it 'trips from DB are equal to imported' do
+      expect(Trip.all.map(&:to_h).sort_by(&:to_s)).to eq trip_from_file.sort_by(&:to_s)
+    end    
+  end
+
+  it 'save trips in DB' do
+    expect { ImportTripsService.call('fixtures/example.json') }.to change { Trip.count }.by(10)
+  end
+  
+  it '1000 trips perform under 2 sec' do
+    expect { ImportTripsService.call('fixtures/small.json') }.to perform_under(2).sec
+  end
+end
diff --git a/spec/spec_helper.rb b/spec/spec_helper.rb
new file mode 100644
index 00000000..9fe9c528
--- /dev/null
+++ b/spec/spec_helper.rb
@@ -0,0 +1,83 @@
+require 'rspec-benchmark'
+#
+# See https://rubydoc.info/gems/rspec-core/RSpec/Core/Configuration
+RSpec.configure do |config|
+  # rspec-expectations config goes here. You can use an alternate
+  # assertion/expectation library such as wrong or the stdlib/minitest
+  # assertions if you prefer.
+  config.expect_with :rspec do |expectations|
+    # This option will default to `true` in RSpec 4. It makes the `description`
+    # and `failure_message` of custom matchers include text for helper methods
+    # defined using `chain`, e.g.:
+    #     be_bigger_than(2).and_smaller_than(4).description
+    #     # => "be bigger than 2 and smaller than 4"
+    # ...rather than:
+    #     # => "be bigger than 2"
+    expectations.include_chain_clauses_in_custom_matcher_descriptions = true
+  end
+
+  # rspec-mocks config goes here. You can use an alternate test double
+  # library (such as bogus or mocha) by changing the `mock_with` option here.
+  config.mock_with :rspec do |mocks|
+    # Prevents you from mocking or stubbing a method that does not exist on
+    # a real object. This is generally recommended, and will default to
+    # `true` in RSpec 4.
+    mocks.verify_partial_doubles = true
+  end
+
+  # This option will default to `:apply_to_host_groups` in RSpec 4 (and will
+  # have no way to turn it off -- the option exists only for backwards
+  # compatibility in RSpec 3). It causes shared context metadata to be
+  # inherited by the metadata hash of host groups and examples, rather than
+  # triggering implicit auto-inclusion in groups with matching metadata.
+  config.shared_context_metadata_behavior = :apply_to_host_groups
+
+# The settings below are suggested to provide a good initial experience
+# with RSpec, but feel free to customize to your heart's content.
+=begin
+  # This allows you to limit a spec run to individual examples or groups
+  # you care about by tagging them with `:focus` metadata. When nothing
+  # is tagged with `:focus`, all examples get run. RSpec also provides
+  # aliases for `it`, `describe`, and `context` that include `:focus`
+  # metadata: `fit`, `fdescribe` and `fcontext`, respectively.
+  config.filter_run_when_matching :focus
+
+  # Allows RSpec to persist some state between runs in order to support
+  # the `--only-failures` and `--next-failure` CLI options. We recommend
+  # you configure your source control system to ignore this file.
+  config.example_status_persistence_file_path = "spec/examples.txt"
+
+  # Limits the available syntax to the non-monkey patched syntax that is
+  # recommended. For more details, see:
+  # https://rspec.info/features/3-12/rspec-core/configuration/zero-monkey-patching-mode/
+  config.disable_monkey_patching!
+
+  # Many RSpec users commonly either run the entire suite or an individual
+  # file, and it's useful to allow more verbose output when running an
+  # individual spec file.
+  if config.files_to_run.one?
+    # Use the documentation formatter for detailed output,
+    # unless a formatter has already been configured
+    # (e.g. via a command-line flag).
+    config.default_formatter = "doc"
+  end
+
+  # Print the 10 slowest examples and example groups at the
+  # end of the spec run, to help surface which specs are running
+  # particularly slow.
+  config.profile_examples = 10
+
+  # Run specs in random order to surface order dependencies. If you find an
+  # order dependency and want to debug it, you can fix the order by providing
+  # the seed, which is printed after each run.
+  #     --seed 1234
+  config.order = :random
+
+  # Seed global randomization in this process using the `--seed` CLI option.
+  # Setting this allows you to use `--seed` to deterministically reproduce
+  # test failures related to randomization by passing the same `--seed` value
+  # as the one that triggered the failure.
+  Kernel.srand config.seed
+=end
+  config.include RSpec::Benchmark::Matchers
+end