diff --git a/lessons/220/deploy/ruby-app/0-config.yaml b/lessons/220/deploy/ruby-app/0-config.yaml
new file mode 100644
index 000000000..c3b66c614
--- /dev/null
+++ b/lessons/220/deploy/ruby-app/0-config.yaml
@@ -0,0 +1,23 @@
+---
+apiVersion: v1
+kind: ConfigMap
+metadata:
+  name: ruby-app
+  namespace: default
+data:
+  database.yml: |
+    default: &default
+      adapter: postgresql
+      encoding: unicode
+      timeout: 5000
+      host: postgresql.antonputra.pvt
+      database: mydb
+      pool: 50
+      username: rails
+      password: devops123
+
+    development:
+      !!merge <<: *default
+
+    production:
+      !!merge <<: *default
diff --git a/lessons/220/deploy/ruby-app/1-deployment.yaml b/lessons/220/deploy/ruby-app/1-deployment.yaml
new file mode 100644
index 000000000..17652eae5
--- /dev/null
+++ b/lessons/220/deploy/ruby-app/1-deployment.yaml
@@ -0,0 +1,86 @@
+---
+apiVersion: apps/v1
+kind: Deployment
+metadata:
+  name: ruby-app
+  namespace: default
+spec:
+  replicas: 2
+  strategy:
+    type: Recreate
+  selector:
+    matchLabels:
+      app: ruby-app
+  template:
+    metadata:
+      labels:
+        app: ruby-app
+    spec:
+      terminationGracePeriodSeconds: 0
+      initContainers:
+      - name: migration
+        image: aputra/ruby-app-220:v5
+        command: ['sh', '-c', "/rails/bin/rake db:migrate"]
+        volumeMounts:
+        - name: config
+          mountPath: /rails/db/config.yml
+          subPath: config.yml
+      containers:
+      - name: ruby-app
+        image: aputra/ruby-app-220:v5
+        ports:
+        - name: http
+          containerPort: 8080
+        - name: WORKERS_NUM
+          value: "2" # 0 for single-mode
+        - name: RAILS_MAX_THREADS
+          value: "2"
+        resources:
+          requests:
+            memory: 512Mi
+            cpu: 750m
+          limits:
+            memory: 512Mi
+            cpu: 1000m
+        readinessProbe:
+          httpGet:
+            path: /up
+            port: http
+        livenessProbe:
+          httpGet:
+            path: /up
+            port: http
+        volumeMounts:
+        - name: config
+          mountPath: /rails/db/config.yml
+          subPath: config.yml
+      volumes:
+      - name: config
+        configMap:
+          name: ruby-app
+      tolerations:
+      - effect: NoSchedule
+        operator: Exists
+      affinity:
+        podAffinity:
+          requiredDuringSchedulingIgnoredDuringExecution:
+          - labelSelector:
+              matchExpressions:
+              - key: app
+                operator: In
+                values:
+                - ruby-app
+            topologyKey: "kubernetes.io/hostname"
+        nodeAffinity:
+          requiredDuringSchedulingIgnoredDuringExecution:
+            nodeSelectorTerms:
+            - matchExpressions:
+              - key: node
+                operator: In
+                values:
+                - general
+            - matchExpressions:
+              - key: kubernetes.io/arch
+                operator: In
+                values:
+                - amd64
diff --git a/lessons/220/deploy/ruby-app/2-service.yaml b/lessons/220/deploy/ruby-app/2-service.yaml
new file mode 100644
index 000000000..5aa99e6b7
--- /dev/null
+++ b/lessons/220/deploy/ruby-app/2-service.yaml
@@ -0,0 +1,14 @@
+---
+apiVersion: v1
+kind: Service
+metadata:
+  name: ruby-app
+  namespace: default
+spec:
+  ports:
+  - name: http
+    port: 8080
+    targetPort: http
+  selector:
+    app: ruby-app
+  type: ClusterIP
diff --git a/lessons/220/deploy/ruby-app/3-pod-monitor.yaml b/lessons/220/deploy/ruby-app/3-pod-monitor.yaml
new file mode 100644
index 000000000..f12ce1ee4
--- /dev/null
+++ b/lessons/220/deploy/ruby-app/3-pod-monitor.yaml
@@ -0,0 +1,17 @@
+---
+apiVersion: monitoring.coreos.com/v1
+kind: PodMonitor
+metadata:
+  name: ruby-app
+  namespace: monitoring
+  labels:
+    prometheus: main
+spec:
+  namespaceSelector:
+    matchNames:
+    - default
+  selector:
+    matchLabels:
+      app: ruby-app
+  podMetricsEndpoints:
+  - port: http
diff --git a/lessons/220/deploy/ruby-app/4-client-pod-monitor.yaml b/lessons/220/deploy/ruby-app/4-client-pod-monitor.yaml
new file mode 100644
index 000000000..9952e0301
--- /dev/null
+++ b/lessons/220/deploy/ruby-app/4-client-pod-monitor.yaml
@@ -0,0 +1,17 @@
+---
+apiVersion: monitoring.coreos.com/v1
+kind: PodMonitor
+metadata:
+  name: rails-client
+  namespace: monitoring
+  labels:
+    prometheus: main
+spec:
+  namespaceSelector:
+    matchNames:
+    - default
+  selector:
+    matchLabels:
+      app: rails-client
+  podMetricsEndpoints:
+  - port: metrics
diff --git a/lessons/220/ruby-app/.dockerignore b/lessons/220/ruby-app/.dockerignore
new file mode 100644
index 000000000..7f5a804c3
--- /dev/null
+++ b/lessons/220/ruby-app/.dockerignore
@@ -0,0 +1,42 @@
+# See https://docs.docker.com/engine/reference/builder/#dockerignore-file for more about ignoring files.
+
+# Ignore git directory.
+/.git/
+/.gitignore
+
+# Ignore bundler config.
+/.bundle
+
+# Ignore all environment files (except templates).
+/.env*
+!/.env*.erb
+
+# Ignore all default key files.
+/config/master.key
+/config/credentials/*.key
+
+# Ignore all logfiles and tempfiles.
+/log/*
+/tmp/*
+!/log/.keep
+!/tmp/.keep
+
+# Ignore pidfiles, but keep the directory.
+/tmp/pids/*
+!/tmp/pids/.keep
+
+# Ignore storage (uploaded files in development and any SQLite databases).
+/storage/*
+!/storage/.keep
+/tmp/storage/*
+!/tmp/storage/.keep
+
+# Ignore CI service files.
+/.github
+
+# Ignore development files
+/.devcontainer
+
+# Ignore Docker-related files
+/.dockerignore
+/Dockerfile*
diff --git a/lessons/220/ruby-app/.gitattributes b/lessons/220/ruby-app/.gitattributes
new file mode 100644
index 000000000..8dc432343
--- /dev/null
+++ b/lessons/220/ruby-app/.gitattributes
@@ -0,0 +1,9 @@
+# See https://git-scm.com/docs/gitattributes for more about git attribute files.
+
+# Mark the database schema as having been generated.
+db/schema.rb linguist-generated
+
+# Mark any vendored files as having been vendored.
+vendor/* linguist-vendored
+config/credentials/*.yml.enc diff=rails_credentials
+config/credentials.yml.enc diff=rails_credentials
diff --git a/lessons/220/ruby-app/.gitignore b/lessons/220/ruby-app/.gitignore
new file mode 100644
index 000000000..b637b08c7
--- /dev/null
+++ b/lessons/220/ruby-app/.gitignore
@@ -0,0 +1,34 @@
+# See https://help.github.com/articles/ignoring-files for more about ignoring files.
+#
+# Temporary files generated by your text editor or operating system
+# belong in git's global ignore instead:
+# `$XDG_CONFIG_HOME/git/ignore` or `~/.config/git/ignore`
+
+# Ignore bundler config.
+/.bundle
+/.idea
+
+# Ignore all environment files (except templates).
+/.env*
+!/.env*.erb
+
+# Ignore all logfiles and tempfiles.
+/log/*
+/tmp/*
+!/log/.keep
+!/tmp/.keep
+
+# Ignore pidfiles, but keep the directory.
+/tmp/pids/*
+!/tmp/pids/
+!/tmp/pids/.keep
+
+# Ignore storage (uploaded files in development and any SQLite databases).
+/storage/*
+!/storage/.keep
+/tmp/storage/*
+!/tmp/storage/
+!/tmp/storage/.keep
+
+# Ignore master key for decrypting credentials and more.
+/config/master.key
diff --git a/lessons/220/ruby-app/.ruby-version b/lessons/220/ruby-app/.ruby-version
new file mode 100644
index 000000000..f13c6f452
--- /dev/null
+++ b/lessons/220/ruby-app/.ruby-version
@@ -0,0 +1 @@
+ruby-3.3.5
diff --git a/lessons/220/ruby-app/Dockerfile b/lessons/220/ruby-app/Dockerfile
new file mode 100644
index 000000000..2b98b6070
--- /dev/null
+++ b/lessons/220/ruby-app/Dockerfile
@@ -0,0 +1,59 @@
+# syntax = docker/dockerfile:1
+
+# This Dockerfile is designed for production, not development. Use with Kamal or build'n'run by hand:
+# docker build -t ruby-app .
+# docker run -d -p 8080:8080 --name ruby-app ruby-app
+
+# Make sure RUBY_VERSION matches the Ruby version in .ruby-version
+ARG RUBY_VERSION=3.3.5
+FROM docker.io/library/ruby:$RUBY_VERSION-slim AS base
+
+# Rails app lives here
+WORKDIR /rails
+
+# Install base packages
+RUN apt-get update -qq && \
+    apt-get install --no-install-recommends -y curl libjemalloc2 libvips sqlite3 libpq-dev && \
+    rm -rf /var/lib/apt/lists /var/cache/apt/archives
+
+# Set production environment
+ENV RAKE_ENV="production" \
+    BUNDLE_DEPLOYMENT="1" \
+    BUNDLE_PATH="/usr/local/bundle" \
+    BUNDLE_WITHOUT="development"
+
+# Throw-away build stage to reduce size of final image
+FROM base AS build
+
+# Install packages needed to build gems
+RUN apt-get update -qq && \
+    apt-get install --no-install-recommends -y build-essential git pkg-config && \
+    rm -rf /var/lib/apt/lists /var/cache/apt/archives
+
+# Install application gems
+COPY Gemfile Gemfile.lock ./
+RUN bundle install && \
+    rm -rf ~/.bundle/ "${BUNDLE_PATH}"/ruby/*/cache "${BUNDLE_PATH}"/ruby/*/bundler/gems/*/.git
+
+# Copy application code
+COPY . .
+
+# Final stage for app image
+FROM base
+
+# Copy built artifacts: gems, application
+COPY --from=build "${BUNDLE_PATH}" "${BUNDLE_PATH}"
+COPY --from=build /rails /rails
+
+# Run and own only the runtime files as a non-root user for security
+RUN groupadd --system --gid 1000 rails && \
+    useradd rails --uid 1000 --gid 1000 --create-home --shell /bin/bash && \
+    chown -R rails:rails db tmp
+USER 1000:1000
+
+# Entrypoint prepares the database.
+ENTRYPOINT ["/rails/bin/docker-entrypoint"]
+
+# Start the server by default, this can be overwritten at runtime
+EXPOSE 8080
+CMD ["bin/iodine", "-p 8080", "config.ru"]
diff --git a/lessons/220/ruby-app/Gemfile b/lessons/220/ruby-app/Gemfile
new file mode 100644
index 000000000..251297ce2
--- /dev/null
+++ b/lessons/220/ruby-app/Gemfile
@@ -0,0 +1,13 @@
+# frozen_string_literal: true
+
+source 'https://rubygems.org'
+
+gem 'connection_pool'
+gem 'pg'
+gem 'rake'
+gem 'standalone_migrations', require: false
+
+gem 'oj'
+gem 'prometheus-client'
+gem 'rack'
+gem 'rage-iodine'
diff --git a/lessons/220/ruby-app/README.md b/lessons/220/ruby-app/README.md
new file mode 100644
index 000000000..cfe57e741
--- /dev/null
+++ b/lessons/220/ruby-app/README.md
@@ -0,0 +1,81 @@
+# README
+
+Basic Ruby application. 25x faster than Rails on my Mac M1.
+
+To setup database run the following commands:
+```bash
+bin/rake db:create
+bin/rake db:migrate
+```
+
+To run the server:
+```bash
+bin/iodine -p 8080
+```
+
+Defaults
+```bash
+WORKERS_NUM=2
+RAILS_MAX_THREADS=2
+
+```
+
+### Local benchmark
+
+#### `rails-app`
+```bash
+WORKERS_NUM=2 RAILS_MAX_THREADS=2 RAILS_ENV=production rs
+wrk -c 10 -t 2 -d 10 --latency http://localhost:8080/api/devices
+Running 10s test @ http://localhost:8080/api/devices
+  2 threads and 10 connections
+  Thread Stats   Avg      Stdev     Max   +/- Stdev
+    Latency     2.12ms  846.12us  31.20ms   94.80%
+    Req/Sec     2.42k   239.12     2.66k    88.12%
+  Latency Distribution
+     50%    1.94ms
+     75%    2.17ms
+     90%    2.63ms
+     99%    5.35ms
+  48603 requests in 10.10s, 46.07MB read
+Requests/sec:   4811.04
+Transfer/sec:      4.56MB
+```
+
+#### `ruby-app`
+```bash
+WORKERS_NUM=2 RAILS_MAX_THREADS=2 bin/iodine -p 8080 config.ru
+wrk -c 10 -t 2 -d 10 --latency http://localhost:8080/api/devices
+Running 10s test @ http://localhost:8080/api/devices
+  2 threads and 10 connections
+  Thread Stats   Avg      Stdev     Max   +/- Stdev
+    Latency   142.99us  660.05us  21.06ms   99.01%
+    Req/Sec    48.48k     9.07k   60.82k    63.00%
+  Latency Distribution
+     50%   83.00us
+     75%  112.00us
+     90%  160.00us
+     99%  798.00us
+  965345 requests in 10.01s, 613.14MB read
+Requests/sec:  96422.17
+Transfer/sec:     61.24MB
+```
+
+#### `ruby-app` with docker
+```bash
+docker build -t ruby-app .
+docker run --rm -p 8080:8080 --name ruby-app ruby-app
+wrk -c 10 -t 2 -d 10 --latency http://localhost:8080/api/devices
+Running 10s test @ http://localhost:8080/api/devices
+  2 threads and 10 connections
+  Thread Stats   Avg      Stdev     Max   +/- Stdev
+    Latency   785.27us    3.26ms  62.81ms   97.92%
+    Req/Sec    12.66k     3.14k   15.44k    84.50%
+  Latency Distribution
+     50%  351.00us
+     75%  430.00us
+     90%  614.00us
+     99%   12.92ms
+  251840 requests in 10.00s, 159.96MB read
+Requests/sec:  25176.72
+Transfer/sec:     15.99MB
+```
diff --git a/lessons/220/ruby-app/Rakefile b/lessons/220/ruby-app/Rakefile
new file mode 100644
index 000000000..4c1375c5e
--- /dev/null
+++ b/lessons/220/ruby-app/Rakefile
@@ -0,0 +1,4 @@
+# frozen_string_literal: true
+
+require 'standalone_migrations'
+StandaloneMigrations::Tasks.load_tasks
diff --git a/lessons/220/ruby-app/bin/docker-entrypoint b/lessons/220/ruby-app/bin/docker-entrypoint
new file mode 100755
index 000000000..cbb10b281
--- /dev/null
+++ b/lessons/220/ruby-app/bin/docker-entrypoint
@@ -0,0 +1,8 @@
+#!/bin/bash -e
+
+# Enable jemalloc for reduced memory usage and latency.
+if [ -z "${LD_PRELOAD+x}" ] && [ -f /usr/lib/*/libjemalloc.so.2 ]; then
+  export LD_PRELOAD="$(echo /usr/lib/*/libjemalloc.so.2)"
+fi
+
+exec "${@}"
diff --git a/lessons/220/ruby-app/bin/iodine b/lessons/220/ruby-app/bin/iodine
new file mode 100755
index 000000000..70c6b50da
--- /dev/null
+++ b/lessons/220/ruby-app/bin/iodine
@@ -0,0 +1,27 @@
+#!/usr/bin/env ruby
+# frozen_string_literal: true
+
+#
+# This file was generated by Bundler.
+#
+# The application 'iodine' is installed as part of a gem, and
+# this file is here to facilitate running it.
+#
+
+ENV['BUNDLE_GEMFILE'] ||= File.expand_path('../Gemfile', __dir__)
+
+bundle_binstub = File.expand_path('bundle', __dir__)
+
+if File.file?(bundle_binstub)
+  if File.read(bundle_binstub, 300).include?('This file was generated by Bundler')
+    load(bundle_binstub)
+  else
+    abort("Your `bin/bundle` was not generated by Bundler, so this binstub cannot run.
+Replace `bin/bundle` by running `bundle binstubs bundler --force`, then run this command again.")
+  end
+end
+
+require 'rubygems'
+require 'bundler/setup'
+
+load Gem.bin_path('rage-iodine', 'iodine')
diff --git a/lessons/220/ruby-app/bin/rake b/lessons/220/ruby-app/bin/rake
new file mode 100755
index 000000000..1ffe17657
--- /dev/null
+++ b/lessons/220/ruby-app/bin/rake
@@ -0,0 +1,28 @@
+#!/usr/bin/env ruby
+# frozen_string_literal: true
+
+#
+# This file was generated by Bundler.
+#
+# The application 'rake' is installed as part of a gem, and
+# this file is here to facilitate running it.
+#
+
+ENV['BUNDLE_GEMFILE'] ||= File.expand_path('../Gemfile', __dir__)
+ENV['RAKE_ENV'] ||= 'production'
+
+bundle_binstub = File.expand_path('bundle', __dir__)
+
+if File.file?(bundle_binstub)
+  if File.read(bundle_binstub, 300).include?('This file was generated by Bundler')
+    load(bundle_binstub)
+  else
+    abort("Your `bin/bundle` was not generated by Bundler, so this binstub cannot run.
+Replace `bin/bundle` by running `bundle binstubs bundler --force`, then run this command again.")
+  end
+end
+
+require 'rubygems'
+require 'bundler/setup'
+
+load Gem.bin_path('rake', 'rake')
diff --git a/lessons/220/ruby-app/config.ru b/lessons/220/ruby-app/config.ru
new file mode 100644
index 000000000..730bd7ec1
--- /dev/null
+++ b/lessons/220/ruby-app/config.ru
@@ -0,0 +1,26 @@
+# frozen_string_literal: true
+
+require 'connection_pool'
+require 'iodine'
+require 'oj'
+require 'pg'
+require 'prometheus/middleware/exporter'
+require 'rack'
+require 'yaml'
+
+require_relative 'src/app'
+
+RubyVM::YJIT.enable
+Iodine.threads = ENV.fetch('RAILS_MAX_THREADS', 2).to_i
+Iodine.workers = ENV.fetch('WORKERS_NUM', 2).to_i
+Oj.default_options = { mode: :compat }
+pg_conf = YAML.load(File.read('db/config.yml'), aliases: true)['production']
+PG_POOL = ConnectionPool.new(size: Iodine.threads * Iodine.workers, timeout: 5) do
+  PG.connect(pg_conf['host'], pg_conf['port'], nil, nil, pg_conf['database'], pg_conf['username'], pg_conf['password'])
+end
+
+# Enable if http metrics are required
+# use Prometheus::Middleware::Collector
+use Prometheus::Middleware::Exporter
+
+run App.new
diff --git a/lessons/220/ruby-app/db/config.yml b/lessons/220/ruby-app/db/config.yml
new file mode 100644
index 000000000..01535dbc2
--- /dev/null
+++ b/lessons/220/ruby-app/db/config.yml
@@ -0,0 +1,13 @@
+---
+default: &default
+  adapter: postgresql
+  host: localhost
+  database: putratest
+  username: appodeal
+  password: pass
+
+development:
+  <<: *default
+
+production:
+  <<: *default
diff --git a/lessons/220/ruby-app/db/migrate/20241028151432_create_devices.rb b/lessons/220/ruby-app/db/migrate/20241028151432_create_devices.rb
new file mode 100644
index 000000000..0dc11ef0d
--- /dev/null
+++ b/lessons/220/ruby-app/db/migrate/20241028151432_create_devices.rb
@@ -0,0 +1,13 @@
+# frozen_string_literal: true
+
+class CreateDevices < ActiveRecord::Migration[7.2]
+  def change
+    create_table :devices do |t|
+      t.string :uuid
+      t.string :mac
+      t.string :firmware
+
+      t.timestamps
+    end
+  end
+end
diff --git a/lessons/220/ruby-app/db/schema.rb b/lessons/220/ruby-app/db/schema.rb
new file mode 100644
index 000000000..b6d7026fc
--- /dev/null
+++ b/lessons/220/ruby-app/db/schema.rb
@@ -0,0 +1,26 @@
+# frozen_string_literal: true
+
+# This file is auto-generated from the current state of the database. Instead
+# of editing this file, please use the migrations feature of Active Record to
+# incrementally modify your database, and then regenerate this schema definition.
+#
+# This file is the source Rails uses to define your schema when running `bin/rails
+# db:schema:load`. When creating a new database, `bin/rails db:schema:load` tends to
+# be faster and is potentially less error prone than running all of your
+# migrations from scratch. Old migrations may fail to apply correctly if those
+# migrations use external dependencies or application code.
+#
+# It's strongly recommended that you check this file into your version control system.
+
+ActiveRecord::Schema[8.0].define(version: 20_241_028_151_432) do
+  # These are extensions that must be enabled in order to support this database
+  enable_extension 'pg_catalog.plpgsql'
+
+  create_table 'devices', force: :cascade do |t|
+    t.string 'uuid'
+    t.string 'mac'
+    t.string 'firmware'
+    t.datetime 'created_at', null: false
+    t.datetime 'updated_at', null: false
+  end
+end
diff --git a/lessons/220/ruby-app/db/seeds.rb b/lessons/220/ruby-app/db/seeds.rb
new file mode 100644
index 000000000..0f162112e
--- /dev/null
+++ b/lessons/220/ruby-app/db/seeds.rb
@@ -0,0 +1,11 @@
+# frozen_string_literal: true
+
+# This file should ensure the existence of records required to run the application in every environment (production,
+# development, test). The code here should be idempotent so that it can be executed at any point in every environment.
+# The data can then be loaded with the bin/rails db:seed command (or created alongside the database with db:setup).
+#
+# Example:
+#
+#   ["Action", "Comedy", "Drama", "Horror"].each do |genre_name|
+#     MovieGenre.find_or_create_by!(name: genre_name)
+#   end
diff --git a/lessons/220/ruby-app/src/app.rb b/lessons/220/ruby-app/src/app.rb
new file mode 100644
index 000000000..6d922ad63
--- /dev/null
+++ b/lessons/220/ruby-app/src/app.rb
@@ -0,0 +1,30 @@
+# frozen_string_literal: true
+
+require_relative 'device'
+
+class App
+  def call(env)
+    case env['PATH_INFO']
+    when '/api/devices'
+      if env['REQUEST_METHOD'] == 'GET'
+        response(Device.list, 200)
+      else
+        begin
+          device = Device.create(Oj.load(env['rack.input'].read))
+
+          response(device.to_h, 201)
+        rescue StandardError => e
+          response({ 'message' => e.message }, 400)
+        end
+      end
+    when '/up'
+      response({ 'message' => 'OK' }, 200)
+    else
+      response({ 'message' => 'Not Found' }, 404)
+    end
+  end
+
+  def response(data, status)
+    [status, { 'Content-Type' => 'application/json' }, [Oj.dump(data)]]
+  end
+end
diff --git a/lessons/220/ruby-app/src/device.rb b/lessons/220/ruby-app/src/device.rb
new file mode 100644
index 000000000..2a95b7c56
--- /dev/null
+++ b/lessons/220/ruby-app/src/device.rb
@@ -0,0 +1,36 @@
+# frozen_string_literal: true
+
+require 'securerandom'
+
+require_relative 'prometheus_client'
+
+Device = Struct.new(:id, :uuid, :mac, :firmware, :created_at, :updated_at, keyword_init: true) do
+  def self.list
+    [
+      { 'id' => 1, 'uuid' => '9add349c-c35c-4d32-ab0f-53da1ba40a2a', 'mac' => '5F-33-CC-1F-43-82', 'firmware' => '2.1.6', 'created_at' => '2024-5-28T15:21:51.137Z', 'updated_at' => '2024-5-28T15:21:51.137Z' },
+      { 'id' => 2, 'uuid' => 'd2293412-36eb-46e7-9231-af7e9249fffe', 'mac' => 'E7-34-96-33-0C-4C', 'firmware' => '1.0.3', 'created_at' => '2024-01-28T15:20:51.137Z', 'updated_at' => '2024-01-28T15:20:51.137Z' },
+      { 'id' => 3, 'uuid' => 'eee58ca8-ca51-47a5-ab48-163fd0e44b77', 'mac' => '68-93-9B-B5-33-B9', 'firmware' => '4.3.1', 'created_at' => '2024-8-28T15:18:21.137Z', 'updated_at' => '2024-8-28T15:18:21.137Z' }
+    ]
+  end
+
+  def self.create(params)
+    now = Time.now
+    uuid = SecureRandom.uuid
+    device = new(uuid: uuid, mac: params['mac'], firmware: params['firmware'], created_at: now, updated_at: now)
+
+    sql = <<~SQL
+      INSERT INTO "devices" ("uuid", "mac", "firmware", "created_at", "updated_at")
+      VALUES ('#{device.uuid}', '#{device.mac}', '#{device.firmware}', '#{device.created_at}', '#{device.updated_at}')
+      RETURNING "id"
+    SQL
+
+    start = Process.clock_gettime(Process::CLOCK_MONOTONIC)
+    PG_POOL.with do |conn|
+      device.id = conn.exec(sql).first['id']
+    end
+    duration = Process.clock_gettime(Process::CLOCK_MONOTONIC) - start
+    PrometheusClient.create_device_histogram.observe(duration, labels: { op: 'db' })
+
+    device
+  end
+end
diff --git a/lessons/220/ruby-app/src/prometheus_client.rb b/lessons/220/ruby-app/src/prometheus_client.rb
new file mode 100644
index 000000000..e925a6b08
--- /dev/null
+++ b/lessons/220/ruby-app/src/prometheus_client.rb
@@ -0,0 +1,52 @@
+# frozen_string_literal: true
+
+require 'prometheus/client'
+
+class PrometheusClient
+  BUCKETS = [
+    0.00001, 0.000015, 0.00002, 0.000025, 0.00003, 0.000035, 0.00004, 0.000045,
+    0.00005, 0.000055, 0.00006, 0.000065, 0.00007, 0.000075, 0.00008, 0.000085,
+    0.00009, 0.000095, 0.0001, 0.000101, 0.000102, 0.000103, 0.000104, 0.000105,
+    0.000106, 0.000107, 0.000108, 0.000109, 0.00011, 0.000111, 0.000112, 0.000113,
+    0.000114, 0.000115, 0.000116, 0.000117, 0.000118, 0.000119, 0.00012, 0.000121,
+    0.000122, 0.000123, 0.000124, 0.000125, 0.000126, 0.000127, 0.000128,
+    0.000129, 0.00013, 0.000131, 0.000132, 0.000133, 0.000134, 0.000135, 0.000136,
+    0.000137, 0.000138, 0.000139, 0.00014, 0.000141, 0.000142, 0.000143, 0.000144,
+    0.000145, 0.000146, 0.000147, 0.000148, 0.000149, 0.00015, 0.000151, 0.000152,
+    0.000153, 0.000154, 0.000155, 0.000156, 0.000157, 0.000158, 0.000159, 0.00016,
+    0.000161, 0.000162, 0.000163, 0.000164, 0.000165, 0.000166, 0.000167,
+    0.000168, 0.000169, 0.00017, 0.000171, 0.000172, 0.000173, 0.000174, 0.000175,
+    0.000176, 0.000177, 0.000178, 0.000179, 0.00018, 0.000181, 0.000182, 0.000183,
+    0.000184, 0.000185, 0.000186, 0.000187, 0.000188, 0.000189, 0.00019, 0.000191,
+    0.000192, 0.000193, 0.000194, 0.000195, 0.000196, 0.000197, 0.000198,
+    0.000199, 0.0002, 0.00021, 0.00022, 0.00023, 0.00024, 0.00025, 0.00026,
+    0.00027, 0.00028, 0.00029, 0.0003, 0.00031, 0.00032, 0.00033, 0.00034,
+    0.00035, 0.00036, 0.00037, 0.00038, 0.00039, 0.0004, 0.00041, 0.00042,
+    0.00043, 0.00044, 0.00045, 0.00046, 0.00047, 0.00048, 0.00049, 0.0005,
+    0.00051, 0.00052, 0.00053, 0.00054, 0.00055, 0.00056, 0.00057, 0.00058,
+    0.00059, 0.0006, 0.00061, 0.00062, 0.00063, 0.00064, 0.00065, 0.00066,
+    0.00067, 0.00068, 0.00069, 0.0007, 0.00071, 0.00072, 0.00073, 0.00074,
+    0.00075, 0.00076, 0.00077, 0.00078, 0.00079, 0.0008, 0.00081, 0.00082,
+    0.00083, 0.00084, 0.00085, 0.00086, 0.00087, 0.00088, 0.00089, 0.0009,
+    0.00091, 0.00092, 0.00093, 0.00094, 0.00095, 0.00096, 0.00097, 0.00098,
+    0.00099, 0.001, 0.0015, 0.002, 0.0025, 0.003, 0.0035, 0.004, 0.0045, 0.005,
+    0.0055, 0.006, 0.0065, 0.007, 0.0075, 0.008, 0.0085, 0.009, 0.0095, 0.01,
+    0.015, 0.02, 0.025, 0.03, 0.035, 0.04, 0.045, 0.05, 0.055, 0.06, 0.065, 0.07,
+    0.075, 0.08, 0.085, 0.09, 0.095, 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45,
+    0.5, 0.55, 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9, 0.95, 1.0, 1.5, 2.0, 2.5,
+    3.0, 3.5, 4.0, 4.5, 5.0, 5.5, 6.0, 6.5, 7.0, 7.5, 8.0, 8.5, 9.0, 9.5, 10.0,
+    10.5, 11.0, 11.5, 12.0, 12.5, 13.0, 13.5, 14.0, 14.5, 15.0, 15.5, 16.0, 16.5, 17.0, 17.5
+  ].freeze
+
+  class << self
+    def client
+      @client ||= Prometheus::Client.registry
+    end
+
+    def create_device_histogram
+      @create_device_histogram ||= client.histogram(
+        :myapp_request_duration_seconds, docstring: 'Duration of the request.', labels: [:op], buckets: BUCKETS
+      )
+    end
+  end
+end
diff --git a/lessons/220/ruby-app/tmp/.keep b/lessons/220/ruby-app/tmp/.keep
new file mode 100644
index 000000000..e69de29bb
diff --git a/lessons/220/ruby-app/wrk.lua b/lessons/220/ruby-app/wrk.lua
new file mode 100644
index 000000000..7a3f223cf
--- /dev/null
+++ b/lessons/220/ruby-app/wrk.lua
@@ -0,0 +1,3 @@
+wrk.method = "POST"
+wrk.headers["Content-Type"] = "application/json"
+wrk.body = '{"mac":"5F-33-CC-1F-43-82", "firmware":"2.1.6"}'