diff --git a/lecture_4/homework/app/controllers/mercenaries_controller.rb b/lecture_4/homework/app/controllers/mercenaries_controller.rb
index 9fb11193..4cfe2c59 100644
--- a/lecture_4/homework/app/controllers/mercenaries_controller.rb
+++ b/lecture_4/homework/app/controllers/mercenaries_controller.rb
@@ -1,61 +1,43 @@
 # frozen_string_literal: true
 
-# This controller is written badly on purpose. Please refactor this
 class MercenariesController < ApplicationController
   def index
-    render json: Mercenary.where('available_from < ?', Time.now).all
+    render json: MercenaryQueries.available.all
   end
 
   def show
     render json: mercenary, include: [:warrior]
   end
 
+  def employ_worst
+    mercenary = MercenariesQuery.sort_available_price_ascending.first
+    mercenary_employer.call(mercenary)
+    render json: mercenary, include: [:warrior], status: 201
+  end
+
   def employ_best
-    mercenary = Mercenary.where('available_from < ?', Time.now).order(price: :asc).first # TODO: what about experience?
-    clan = find_clan
-    building = find_building
-    warrior_class = clan.warriors.select('type, count(type) as warriors_count').group(:type).order('warriors_count ASC').first.class
-    warrior = warrior_class.create!(name: mercenary.name, clan: clan, building: building, preferred_weapon_kind: mercenary.preferred_weapon_kind, mercenary: mercenary)
-    create_good_weapon(mercenary)
+    mercenary = MercenariesQuery.sort_available_exp_descending.first
+    mercenary_employer.call(mercenary)
     render json: warrior, include: [:mercenary], status: 201
   end
 
   def employ
-    return unless mercenary.available_from < Time.now
-    clan = find_clan
-    building = find_building
-    warrior_class = clan.warriors.select('type, count(type) as warriors_count').group(:type).order('warriors_count ASC').first.class
-    warrior = warrior_class.create!(name: mercenary.name, clan: clan, building: building, preferred_weapon_kind: mercenary.preferred_weapon_kind, mercenary: mercenary)
-    create_good_weapon(mercenary)
+    mercenary = MercenariesQuery.available.sample
+    mercenary_employer.call(mercenary)
     render json: warrior, include: [:mercenary], status: 201
   end
 
   private
 
-  def mercenary
-    @mercenary ||= Mercenary.find(params[:id])
-  end
-
-  def find_building
-    Building.find(params[:building_id]) if params[:building_id]
+  def mercenary_params
+    params.permit(:name, :expirience, :price, :clan_id, :building_id, :warrior_id)
   end
 
-  def find_clan
-    if params[:clan_id]
-      Clan.find(params[:clan_id])
-    else
-      Clan.order(warriors_count: :desc).first
-    end
+  def mercenary_employer
+    MercenaryEmployer.new(mercenary_params)
   end
 
-  def create_good_weapon(mercenary)
-    case mercenary.preferred_weapon_kind
-    when :melee
-      Weapons::Katana.create!(warrior: mercenary.warrior, range: 2, damage: 25)
-    when :ranged
-      Weapons::Musket.create!(warrior: mercenary.warrior, range: 40, damage: 10)
-    else
-      # TODO: some default?
-    end
+  def mercenary
+    @mercenary ||= MercenaryQueries.find_by_id(params[:id])
   end
 end
diff --git a/lecture_4/homework/app/models/warrior.rb b/lecture_4/homework/app/models/warrior.rb
index e1c06a8f..04c12742 100644
--- a/lecture_4/homework/app/models/warrior.rb
+++ b/lecture_4/homework/app/models/warrior.rb
@@ -22,4 +22,8 @@ def attack
   def null_weapon_check
     weapon || NullWeapon.new
   end
+
+  def mercenary_null_check
+    mercenary || NullMercenary.new
+  end
 end
diff --git a/lecture_4/homework/app/nulls/null_mercenary.rb b/lecture_4/homework/app/nulls/null_mercenary.rb
new file mode 100644
index 00000000..2610d8cb
--- /dev/null
+++ b/lecture_4/homework/app/nulls/null_mercenary.rb
@@ -0,0 +1,19 @@
+# frozen_string_literal: true
+
+class NullMercenary
+  def name
+    'Name has not been initialized'
+  end
+
+  def preffered_weapon_kind
+    'melee'
+  end
+
+  def available_from
+    nil
+  end
+
+  def price
+    nil
+  end
+end
diff --git a/lecture_4/homework/app/queries/buildings_query.rb b/lecture_4/homework/app/queries/buildings_query.rb
new file mode 100644
index 00000000..24ea7579
--- /dev/null
+++ b/lecture_4/homework/app/queries/buildings_query.rb
@@ -0,0 +1,7 @@
+# frozen_string_literal: true
+
+class BuildingsQuery
+  def self.find_by_id(id = nil, relation: Building)
+    id.nil? ? relation.first : relation.find(id)
+  end
+end
diff --git a/lecture_4/homework/app/queries/clans_query.rb b/lecture_4/homework/app/queries/clans_query.rb
new file mode 100644
index 00000000..60e4c213
--- /dev/null
+++ b/lecture_4/homework/app/queries/clans_query.rb
@@ -0,0 +1,7 @@
+# frozen_literal_string: true
+
+class ClansQuery
+  def self.find_by_id(id = nil, relation: Clan)
+    id.nil? ? relation.order(warriors_count: :desc).first : relation.find(id)
+  end
+end
diff --git a/lecture_4/homework/app/queries/mercenaries_query.rb b/lecture_4/homework/app/queries/mercenaries_query.rb
new file mode 100644
index 00000000..c32ad7b0
--- /dev/null
+++ b/lecture_4/homework/app/queries/mercenaries_query.rb
@@ -0,0 +1,19 @@
+# frozen_literal_string: true
+
+class MercenariesQuery
+  def self.find_by_id(id = nil, relation: Mercenary)
+    id.nil? ? relation.first : relation.find(id)
+  end
+
+  def self.sort_exp_descending(relation: Mercenary)
+    relation.order(expirience: :desc)
+  end
+
+  def self.sort_available_exp_descending(relation: available)
+    relation.order(expirience: :desc)
+  end
+
+  def self.sort_available_price_ascending(relation: available)
+    relation.order(price: :asc)
+  end
+end
diff --git a/lecture_4/homework/app/queries/warriors_query.rb b/lecture_4/homework/app/queries/warriors_query.rb
new file mode 100644
index 00000000..57302e68
--- /dev/null
+++ b/lecture_4/homework/app/queries/warriors_query.rb
@@ -0,0 +1,16 @@
+# frozen_string_literal :true
+
+class WarriorsQuery
+  def self.find_by_id(id = nil, relation: Warrior)
+    id.nil? ? relation.first : relation.find(id)
+  end
+
+  def self.belonging_to_clan(clan_id:, relation: Warrior)
+    relation.where(clan_id: clan_id)
+  end
+
+  def self.get_class(relation: Warrior)
+    relation.warriors.select('type, count(type) as warriors_count')
+            .group(:type).oreder('warriors_count ASC').first.class
+  end
+end
diff --git a/lecture_4/homework/app/queries/weapons_query.rb b/lecture_4/homework/app/queries/weapons_query.rb
new file mode 100644
index 00000000..59782348
--- /dev/null
+++ b/lecture_4/homework/app/queries/weapons_query.rb
@@ -0,0 +1,7 @@
+# frozen_string_literal: true
+
+class WeaponsQuery
+  def self.find_by_id(id = nil, relation: Weapon)
+    id.nil? ? relation.first : relation.find(id)
+  end
+end
diff --git a/lecture_4/homework/app/services/mercenary_employer.rb b/lecture_4/homework/app/services/mercenary_employer.rb
new file mode 100644
index 00000000..4aee584d
--- /dev/null
+++ b/lecture_4/homework/app/services/mercenary_employer.rb
@@ -0,0 +1,42 @@
+# frozen_literal_string: true
+
+class MercenaryEmployer
+  def initialize(mercenary_params)
+    @params = mercenary_params
+  end
+
+  def self.call(mercenary)
+    clan = find_clan
+    building = find_building
+    warrior_class = WarriorQuery.get_class
+    warrior_class.create(name: mercenary.name,
+                         clan: clan,
+                         building: building,
+                         preffered_weapon_kind: preffered_weapon_kind,
+                         mercenary: mercenary)
+    create_good_weapon(mercenary)
+  end
+
+  private
+
+  attr_reader :params
+
+  def find_building
+    BuildingsQuery.find_by_id(params[:building_id])
+  end
+
+  def find_clan
+    ClansQuery.find_by_id(params[:clan_id])
+  end
+
+  def create_good_weapon(mercenary)
+    case mercenary.preferred_weapon_kind
+    when :melee
+      Weapons::Katana.create!(warrior: mercenary.warrior, range: 2, damage: 25)
+    when :ranged
+      Weapons::Musket.create!(warrior: mercenary.warrior, range: 40, damage: 10)
+    else
+      NullWeapon.new
+    end
+  end
+end