diff --git a/app/models/urn.rb b/app/models/urn.rb
index e88c85e1..56330c1c 100644
--- a/app/models/urn.rb
+++ b/app/models/urn.rb
@@ -1,41 +1,38 @@
-# == Schema Information
+# frozen_string_literal: true
+
+# Urn represents a Uniform Resource Name (URN) generator.
+# It generates a URN with a fixed prefix and a random alphanumeric suffix.
 #
-# Table name: urns
 #
-#  id         :bigint           not null, primary key
-#  code       :string
-#  prefix     :string
-#  suffix     :integer
-#  created_at :datetime         not null
-#  updated_at :datetime         not null
+# Example:
 #
-class Urn < ApplicationRecord
-  class NoUrnAvailableError < StandardError; end
-
-  PREFIX = "IRP".freeze
-  MAX_SUFFIX = 99_999
-  PADDING_SIZE = MAX_SUFFIX.to_s.size
-  VALID_CODES = {
-    "teacher" => "TE",
-    "salaried_trainee" => "ST",
-  }.freeze
+#   Urn.generate('teacher')          # => "IRPTE12345"
+#   Urn.generate('teacher')          # => "IRPTE12345"
+#   Urn.generate('salaried_trainee') # => "IRPST12345"
+#
+class Urn
+  attr_reader :value
+  attr_writer :suffix
 
-  def self.next(route)
-    code = VALID_CODES.fetch(route)
-    Urn.transaction do
-      urn = find_by!(code:)
-      urn.destroy!
-      urn.to_s
-    end
-  rescue KeyError => e
-    Sentry.capture_exception(e)
-    raise(ArgumentError, "Unknown route #{route}")
-  rescue ActiveRecord::RecordNotFound => e
-    Sentry.capture_exception(e)
-    raise(NoUrnAvailableError, "There no more unique URN available for #{route}")
+  def self.generate(applicant_type)
+    code = applicant_type_code(applicant_type)
+    PREFIX + code + Array.new(LENGTH) { CHARSET.sample }.join
   end
 
-  def to_s
-    [prefix, code, sprintf("%0#{PADDING_SIZE}d", suffix)].join
+  CHARSET = %w[0 1 2 3 4 5 6 7 8 9].freeze
+  PREFIX = "IRP"
+  LENGTH = 5
+  private_constant :CHARSET, :PREFIX, :LENGTH
+
+  def self.applicant_type_code(applicant_type)
+    case applicant_type
+    when "teacher"
+      "TE"
+    when "salaried_trainee"
+      "ST"
+    else
+      raise(ArgumentError, "Invalid applicant type: #{applicant_type}")
+    end
   end
+  private_methods :applicant_type_code
 end
diff --git a/app/services/generate_urns.rb b/app/services/generate_urns.rb
deleted file mode 100644
index a0a33274..00000000
--- a/app/services/generate_urns.rb
+++ /dev/null
@@ -1,62 +0,0 @@
-# Service responsible for the generation of all urns
-# It will save the set of available urns based the current URN format
-# and store it in the database URNs table.
-#
-# The Urn model will then be able to fetch the next available unique and
-# random urn for application submition
-#
-# Example:
-#
-#   Urn.next("teacher")          # => "IRPTE12345"
-#   Urn.next("teacher")          # => "IRPTE12345"
-#   Urn.next("salaried_trainee") # => "IRPST12345"
-#
-class GenerateUrns
-  def self.call
-    return if Urn.count.positive? # Do not override the current urn state
-
-    Urn.transaction do
-      Urn::VALID_CODES.each_value do |code|
-        new(code:).generate
-      end
-    end
-  end
-
-  def initialize(code:)
-    @code = code
-  end
-
-  attr_reader :code
-
-  def generate
-    data = unused_urns.map do |suffix|
-      { prefix: Urn::PREFIX, code: code, suffix: suffix }
-    end
-    Urn.insert_all(data) # rubocop:disable Rails/SkipsModelValidations
-  end
-
-private
-
-  def unused_urns
-    generate_suffixes - existing_suffixes
-  end
-
-  def generate_suffixes
-    Array
-      .new(Urn::MAX_SUFFIX) { _1 }
-      .drop(1)
-      .shuffle!
-  end
-
-  def existing_suffixes
-    route = Urn::VALID_CODES.key(code)
-    Application
-      .where(application_route: route)
-      .pluck(:urn)
-      .map { extract_suffix(_1) }
-  end
-
-  def extract_suffix(urn)
-    urn.match(/\d+/)[0].to_i
-  end
-end
diff --git a/app/services/submit_form.rb b/app/services/submit_form.rb
index a6ccb4d5..28bdbaff 100644
--- a/app/services/submit_form.rb
+++ b/app/services/submit_form.rb
@@ -88,7 +88,7 @@ def create_application
       date_of_entry: form.date_of_entry,
       start_date: form.start_date,
       subject: SubjectStep.new(form).answer.formatted_value,
-      urn: Urn.next(form.application_route),
+      urn: Urn.generate(form.application_route),
       visa_type: form.visa_type,
     )
   end
diff --git a/bin/app-startup.sh b/bin/app-startup.sh
index 9da89774..0df4c416 100755
--- a/bin/app-startup.sh
+++ b/bin/app-startup.sh
@@ -7,8 +7,6 @@ set -e
 
 # run migrations
 bundle exec rails db:migrate
-# Front load urn generation
-bundle exec rake urn:generate
 
 # add seed data in review environment
 if [[ "$RAILS_ENV" = "review" || "$RAILS_ENV" = "development" ]]; then
diff --git a/db/migrate/20230927092305_create_urns.rb b/db/migrate/20230927092305_create_urns.rb
deleted file mode 100644
index e13281c1..00000000
--- a/db/migrate/20230927092305_create_urns.rb
+++ /dev/null
@@ -1,12 +0,0 @@
-class CreateUrns < ActiveRecord::Migration[7.0]
-  def change
-    create_table :urns do |t|
-      t.string :prefix
-      t.string :code
-      t.integer :suffix
-
-      t.timestamps
-    end
-    add_index :urns, :code
-  end
-end
diff --git a/db/migrate/20231009110217_add_application_indexes.rb b/db/migrate/20231009110217_add_application_indexes.rb
new file mode 100644
index 00000000..a1d241ad
--- /dev/null
+++ b/db/migrate/20231009110217_add_application_indexes.rb
@@ -0,0 +1,7 @@
+class AddApplicationIndexes < ActiveRecord::Migration[7.0]
+  def change
+    drop_table :urns
+    add_index :applications, :urn, unique: true
+    add_index :applications, :application_route
+  end
+end
diff --git a/db/schema.rb b/db/schema.rb
index 4d5e00a1..18a49063 100644
--- a/db/schema.rb
+++ b/db/schema.rb
@@ -10,7 +10,7 @@
 #
 # It's strongly recommended that you check this file into your version control system.
 
-ActiveRecord::Schema[7.0].define(version: 2023_10_02_115920) do
+ActiveRecord::Schema[7.0].define(version: 2023_10_09_110217) do
   # These are extensions that must be enabled in order to support this database
   enable_extension "citext"
   enable_extension "plpgsql"
@@ -84,6 +84,8 @@
     t.datetime "standing_data_csv_downloaded_at"
     t.datetime "payroll_csv_downloaded_at"
     t.index ["applicant_id"], name: "index_applications_on_applicant_id"
+    t.index ["application_route"], name: "index_applications_on_application_route"
+    t.index ["urn"], name: "index_applications_on_urn", unique: true
   end
 
   create_table "audits", force: :cascade do |t|
@@ -183,15 +185,6 @@
     t.datetime "updated_at", null: false
   end
 
-  create_table "urns", force: :cascade do |t|
-    t.string "prefix"
-    t.string "code"
-    t.integer "suffix"
-    t.datetime "created_at", null: false
-    t.datetime "updated_at", null: false
-    t.index ["code"], name: "index_urns_on_code"
-  end
-
   create_table "users", force: :cascade do |t|
     t.citext "email"
     t.datetime "created_at", null: false
diff --git a/lib/tasks/urn.rake b/lib/tasks/urn.rake
deleted file mode 100644
index 64c42ccd..00000000
--- a/lib/tasks/urn.rake
+++ /dev/null
@@ -1,10 +0,0 @@
-namespace :urn do
-  desc "generate and randomize unique urns"
-  task generate: :environment do
-    puts "running rake task urn:generate ..."
-    a = Urn.count
-    GenerateUrns.call
-    b = Urn.count
-    puts "#{b - a} URN created"
-  end
-end
diff --git a/spec/factories/applications.rb b/spec/factories/applications.rb
index 712bf90b..49d86172 100644
--- a/spec/factories/applications.rb
+++ b/spec/factories/applications.rb
@@ -31,7 +31,7 @@
     visa_type { VisaStep::VALID_ANSWERS_OPTIONS.reject { _1 == "Other" }.sample }
     date_of_entry { Time.zone.today }
     start_date { 1.month.from_now.to_date }
-    urn { Urn.next(application_route) }
+    urn { Urn.generate(application_route) }
 
     factory :teacher_application do
       application_route { "teacher" }
diff --git a/spec/factories/urns.rb b/spec/factories/urns.rb
deleted file mode 100644
index 5ecebff0..00000000
--- a/spec/factories/urns.rb
+++ /dev/null
@@ -1,18 +0,0 @@
-# == Schema Information
-#
-# Table name: urns
-#
-#  id         :bigint           not null, primary key
-#  code       :string
-#  prefix     :string
-#  suffix     :integer
-#  created_at :datetime         not null
-#  updated_at :datetime         not null
-#
-FactoryBot.define do
-  factory :urn do
-    prefix { "IRP" }
-    code { %w[TE ST].sample }
-    suffix { Array.new(10) { _1 }.sample }
-  end
-end
diff --git a/spec/features/admin_console/applications_list_spec.rb b/spec/features/admin_console/applications_list_spec.rb
index 8cb032cd..85a51dee 100644
--- a/spec/features/admin_console/applications_list_spec.rb
+++ b/spec/features/admin_console/applications_list_spec.rb
@@ -59,8 +59,6 @@
 
   def given_there_are_few_applications
     # Create 2 specific applications for search tests
-    create_list(:urn, 5, code: "TE")
-    create_list(:urn, 5, code: "ST")
     unique_applicant = create(:applicant, given_name: "Unique Given Name", middle_name: "Unique Middle Name", family_name: "Unique Family Name", email_address: "unique@example.com")
     create(:application, applicant: unique_applicant, urn: "Unique Urn 1")
 
@@ -72,16 +70,12 @@ def given_there_are_few_applications
   end
 
   def given_there_is_an_application_that_breached_sla
-    create_list(:urn, 5, code: "TE")
-    create_list(:urn, 5, code: "ST")
     applicant = create(:applicant)
     application = create(:application, applicant:)
     application.application_progress.update(initial_checks_completed_at: 4.days.ago)
   end
 
   def given_there_are_applications_with_different_dates
-    create_list(:urn, 5, code: "TE")
-    create_list(:urn, 5, code: "ST")
     create(:application, application_progress: build(:application_progress, :initial_checks_completed, status: :initial_checks))
     create(:application, application_progress: build(:application_progress, :home_office_checks_completed, status: :home_office_checks))
   end
diff --git a/spec/fixtures/urns.yml b/spec/fixtures/urns.yml
deleted file mode 100644
index e2cfb088..00000000
--- a/spec/fixtures/urns.yml
+++ /dev/null
@@ -1,101 +0,0 @@
-# == Schema Information
-#
-# Table name: urns
-#
-#  id         :bigint           not null, primary key
-#  code       :string
-#  prefix     :string
-#  suffix     :integer
-#  created_at :datetime         not null
-#  updated_at :datetime         not null
-#
-te_one:
-  suffix: 5668
-  prefix: IRP
-  code: TE
-
-te_two:
-  suffix: 21368
-  prefix: IRP
-  code: TE
-
-te_three:
-  suffix: 5
-  prefix: IRP
-  code: TE
-
-te_four:
-  suffix: 76998
-  prefix: IRP
-  code: TE
-
-te_five:
-  suffix: 6559
-  prefix: IRP
-  code: TE
-   
-te_six:
-  suffix: 6
-  prefix: IRP
-  code: TE
-
-te_seven:
-  suffix: 2298
-  prefix: IRP
-  code: TE
-
-te_eight:
-  suffix: 1159
-  prefix: IRP
-  code: TE
- 
-te_nine:
-  suffix: 79298
-  prefix: IRP
-  code: TE
-
-te_ten:
-  suffix: 19549
-  prefix: IRP
-  code: TE
-   
-st_one:
-  suffix: 5668
-  prefix: IRP
-  code: ST
-
-st_two:
-  suffix: 29968
-  prefix: IRP
-  code: ST
-
-st_three:
-  suffix: 5
-  prefix: IRP
-  code: ST
-
-st_four:
-  suffix: 76998
-  prefix: IRP
-  code: ST
-
-st_five:
-  suffix: 6559
-  prefix: IRP
-  code: ST
-   
-st_six:
-  suffix: 6
-  prefix: IRP
-  code: ST
-
-st_seven:
-  suffix: 28
-  prefix: IRP
-  code: ST
-
-st_eight:
-  suffix: 159
-  prefix: IRP
-  code: ST
- 
diff --git a/spec/models/urn_spec.rb b/spec/models/urn_spec.rb
index eb150367..4df75ded 100644
--- a/spec/models/urn_spec.rb
+++ b/spec/models/urn_spec.rb
@@ -1,60 +1,39 @@
-# == Schema Information
-#
-# Table name: urns
-#
-#  id         :bigint           not null, primary key
-#  code       :string
-#  prefix     :string
-#  suffix     :integer
-#  created_at :datetime         not null
-#  updated_at :datetime         not null
-#
+# frozen_string_literal: true
+
 require "rails_helper"
 
 RSpec.describe Urn do
-  describe "next" do
-    subject(:next_urn) { described_class.next(route) }
-
-    context "for application route teacher" do
-      let(:route) { "teacher" }
-
-      before { create(:urn, code: "TE") }
+  subject(:urn) { described_class.generate(applicant_type) }
 
-      it { expect(next_urn).to match(/IRPTE\d{5}/) }
-    end
+  describe ".generate" do
+    context 'when applicant type is "teacher"' do
+      let(:applicant_type) { "teacher" }
 
-    context "for application route salaried_trainee" do
-      let(:route) { "salaried_trainee" }
+      it "generates a URN with the correct prefix and suffix" do
+        expect(urn).to match(/^IRPTE[0-9]{5}$/)
+      end
 
-      before { create(:urn, code: "ST") }
+      it "generates a Urn with a suffix of only characters in the CHARSET" do
+        charset = %w[0 1 2 3 4 5 6 7 8 9]
 
-      it { expect(next_urn).to match(/IRPST\d{5}/) }
+        expect(urn[5..9].chars).to all(be_in(charset))
+      end
     end
 
-    context "when bad application route" do
-      let(:route) { "badroute" }
+    context 'when applicant type is "salaried_trainee"' do
+      let(:applicant_type) { "salaried_trainee" }
 
-      it { expect { next_urn }.to raise_error(ArgumentError) }
+      it "generates a URN with the correct prefix and suffix" do
+        expect(urn).to match(/^IRPST[0-9]{5}$/)
+      end
     end
 
-    context "when there is no more urn available to assign" do
-      let(:route) { "salaried_trainee" }
+    context "when an invalid applicant type is provided" do
+      let(:applicant_type) { "invalid_type" }
 
-      before do
-        allow(described_class).to receive(:find_by!).and_raise(ActiveRecord::RecordNotFound)
+      it "raises an ArgumentError" do
+        expect { urn }.to raise_error(ArgumentError, "Invalid applicant type: invalid_type")
       end
-
-      it { expect { next_urn }.to raise_error(Urn::NoUrnAvailableError) }
     end
   end
-
-  describe ".to_s" do
-    subject(:urn) { described_class.new(prefix:, code:, suffix:) }
-
-    let(:prefix) { "AST" }
-    let(:code) { "FF" }
-    let(:suffix) { 65 }
-
-    it { expect(urn.to_s).to eq("ASTFF00065") }
-  end
 end
diff --git a/spec/rails_helper.rb b/spec/rails_helper.rb
index edfe2b50..6ba490c8 100644
--- a/spec/rails_helper.rb
+++ b/spec/rails_helper.rb
@@ -42,8 +42,7 @@
 end
 RSpec.configure do |config|
   # Remove this line if you're not using ActiveRecord or ActiveRecord fixtures
-  config.fixture_path = Rails.root.join("spec/fixtures")
-  config.global_fixtures = :urns
+  config.fixture_path = Rails.root.join("/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
diff --git a/spec/services/generate_urns_spec.rb b/spec/services/generate_urns_spec.rb
deleted file mode 100644
index cbe58507..00000000
--- a/spec/services/generate_urns_spec.rb
+++ /dev/null
@@ -1,23 +0,0 @@
-require "rails_helper"
-
-RSpec.describe GenerateUrns do
-  describe ".generate" do
-    subject(:generate) { described_class.new(code:).generate }
-
-    before do
-      allow(Urn).to receive(:insert_all)
-      stub_const "Urn::MAX_SUFFIX", 3
-      generate
-    end
-
-    let(:code) { "TE" }
-    let(:expected_data) do
-      [
-        { prefix: "IRP", code: code, suffix: 1 },
-        { prefix: "IRP", code: code, suffix: 2 },
-      ]
-    end
-
-    it { expect(Urn).to have_received(:insert_all).with(match_array(expected_data)) }
-  end
-end
diff --git a/spec/services/submit_form_spec.rb b/spec/services/submit_form_spec.rb
index c7faac40..8606e43f 100644
--- a/spec/services/submit_form_spec.rb
+++ b/spec/services/submit_form_spec.rb
@@ -136,7 +136,7 @@
 
       context "applicant email" do
         before do
-          allow(Urn).to receive(:next).and_return(urn)
+          allow(Urn).to receive(:generate).and_return(urn)
         end
 
         let(:urn) { "SOMEURN" }