diff --git a/app/models/ci/build.rb b/app/models/ci/build.rb
index b8068a22c02ca8541bc9caa6550e6eff671772f9..21dbbae17474f55a7c2b6700b67dde10311432a1 100644
--- a/app/models/ci/build.rb
+++ b/app/models/ci/build.rb
@@ -23,6 +23,7 @@ class Build < CommitStatus
     belongs_to :runner
     belongs_to :trigger_request
     belongs_to :erased_by, class_name: 'User'
+    belongs_to :resource_group, class_name: 'Ci::ResourceGroup', inverse_of: :builds
 
     RUNNER_FEATURES = {
       upload_multiple_artifacts: -> (build) { build.publishes_artifacts_reports? },
@@ -34,6 +35,7 @@ class Build < CommitStatus
     }.freeze
 
     has_one :deployment, as: :deployable, class_name: 'Deployment'
+    has_one :resource, class_name: 'Ci::Resource', inverse_of: :build
     has_many :trace_sections, class_name: 'Ci::BuildTraceSection'
     has_many :trace_chunks, class_name: 'Ci::BuildTraceChunk', foreign_key: :build_id
 
@@ -441,6 +443,15 @@ def has_environment?
       environment.present?
     end
 
+    def requires_resource?
+      Feature.enabled?(:ci_resource_group, project) &&
+        self.resource_group_id.present? && resource.nil?
+    end
+
+    def retains_resource?
+      self.resource_group_id.present? && resource.present?
+    end
+
     def starts_environment?
       has_environment? && self.environment_action == 'start'
     end
diff --git a/app/models/ci/resource.rb b/app/models/ci/resource.rb
new file mode 100644
index 0000000000000000000000000000000000000000..ee5b6546165bb47c4adde08a31468a0b771ed305
--- /dev/null
+++ b/app/models/ci/resource.rb
@@ -0,0 +1,13 @@
+# frozen_string_literal: true
+
+module Ci
+  class Resource < ApplicationRecord
+    extend Gitlab::Ci::Model
+
+    belongs_to :resource_group, class_name: 'Ci::ResourceGroup', inverse_of: :resources
+    belongs_to :build, class_name: 'Ci::Build', inverse_of: :resource
+
+    scope :free, -> { where(build: nil) }
+    scope :retained_by, -> (build) { where(build: build) }
+  end
+end
diff --git a/app/models/ci/resource_group.rb b/app/models/ci/resource_group.rb
new file mode 100644
index 0000000000000000000000000000000000000000..fb562783d3d935dbb832fd12ed91e630ee3532b8
--- /dev/null
+++ b/app/models/ci/resource_group.rb
@@ -0,0 +1,36 @@
+# frozen_string_literal: true
+
+module Ci
+  class ResourceGroup < ApplicationRecord
+    extend Gitlab::Ci::Model
+
+    belongs_to :project, inverse_of: :resource_groups
+
+    has_many :resources, class_name: 'Ci::Resource', inverse_of: :resource_group
+    has_many :builds, class_name: 'Ci::Build', inverse_of: :resource_group
+
+    validates :key,
+      length: { maximum: 255 },
+      format: { with: Gitlab::Regex.environment_name_regex,
+                message: Gitlab::Regex.environment_name_regex_message }
+
+    before_create :ensure_resource
+
+    def retain_resource_for(build)
+      resources.free.limit(1).update_all(build_id: build.id) > 0
+    end
+
+    def release_resource_from(build)
+      resources.retained_by(build).update_all(build_id: nil) > 0
+    end
+
+    private
+
+    def ensure_resource
+      # Currently we only support one resource per group, which means
+      # maximum one build can be set to the resource group, thus builds
+      # belong to the same resource group are executed once at time.
+      self.resources.build if self.resources.empty?
+    end
+  end
+end
diff --git a/app/models/project.rb b/app/models/project.rb
index 84289e1d5acd481c992613b70e85e95343a7596e..eacaaac8a6c20aaa5729e5dfbe9ec361ac0145fb 100644
--- a/app/models/project.rb
+++ b/app/models/project.rb
@@ -285,6 +285,7 @@ class Project < ApplicationRecord
   has_many :pipeline_schedules, class_name: 'Ci::PipelineSchedule'
   has_many :project_deploy_tokens
   has_many :deploy_tokens, through: :project_deploy_tokens
+  has_many :resource_groups, class_name: 'Ci::ResourceGroup', inverse_of: :project
 
   has_one :auto_devops, class_name: 'ProjectAutoDevops', inverse_of: :project, autosave: true
   has_many :custom_attributes, class_name: 'ProjectCustomAttribute'
diff --git a/app/services/ci/retry_build_service.rb b/app/services/ci/retry_build_service.rb
index 7a5e33c61babca3e3a19eb6e3d9612859ec25bba..5abfbd266415b813dccf3bfe25422e26be96778b 100644
--- a/app/services/ci/retry_build_service.rb
+++ b/app/services/ci/retry_build_service.rb
@@ -5,7 +5,7 @@ class RetryBuildService < ::BaseService
     CLONE_ACCESSORS = %i[pipeline project ref tag options name
                          allow_failure stage stage_id stage_idx trigger_request
                          yaml_variables when environment coverage_regex
-                         description tag_list protected needs].freeze
+                         description tag_list protected needs resource_group].freeze
 
     def execute(build)
       reprocess!(build).tap do |new_build|
diff --git a/changelogs/unreleased/ci-resource-group-model.yml b/changelogs/unreleased/ci-resource-group-model.yml
new file mode 100644
index 0000000000000000000000000000000000000000..98bc0159626d302122a0862a538b37e66eb10148
--- /dev/null
+++ b/changelogs/unreleased/ci-resource-group-model.yml
@@ -0,0 +1,5 @@
+---
+title: Add Ci Resource Group models
+merge_request: 20950
+author:
+type: other
diff --git a/db/migrate/20191128145231_add_ci_resource_groups.rb b/db/migrate/20191128145231_add_ci_resource_groups.rb
new file mode 100644
index 0000000000000000000000000000000000000000..0b730e47ddac5251fb679d00208c026b8be6d8ee
--- /dev/null
+++ b/db/migrate/20191128145231_add_ci_resource_groups.rb
@@ -0,0 +1,24 @@
+# frozen_string_literal: true
+
+class AddCiResourceGroups < ActiveRecord::Migration[5.2]
+  DOWNTIME = false
+
+  def change
+    create_table :ci_resource_groups do |t|
+      t.timestamps_with_timezone
+      t.references :project, null: false, index: false, foreign_key: { on_delete: :cascade }
+      t.string :key, null: false, limit: 255
+      t.index %i[project_id key], unique: true
+    end
+
+    create_table :ci_resources do |t|
+      t.timestamps_with_timezone
+      t.references :resource_group, null: false, index: false, foreign_key: { to_table: :ci_resource_groups, on_delete: :cascade }
+      t.references :build, null: true, index: true, foreign_key: { to_table: :ci_builds, on_delete: :nullify }
+      t.index %i[resource_group_id build_id], unique: true
+    end
+
+    add_column :ci_builds, :resource_group_id, :bigint
+    add_column :ci_builds, :waiting_for_resource_at, :datetime_with_timezone
+  end
+end
diff --git a/db/migrate/20191129144631_add_index_to_resource_group_id.rb b/db/migrate/20191129144631_add_index_to_resource_group_id.rb
new file mode 100644
index 0000000000000000000000000000000000000000..0e5a84f094dfc5c8e4e3359ad87cf0be6c04e932
--- /dev/null
+++ b/db/migrate/20191129144631_add_index_to_resource_group_id.rb
@@ -0,0 +1,20 @@
+# frozen_string_literal: true
+
+class AddIndexToResourceGroupId < ActiveRecord::Migration[5.2]
+  include Gitlab::Database::MigrationHelpers
+
+  DOWNTIME = false
+  INDEX_NAME = 'index_for_resource_group'.freeze
+
+  disable_ddl_transaction!
+
+  def up
+    add_concurrent_index :ci_builds, %i[resource_group_id id], where: 'resource_group_id IS NOT NULL', name: INDEX_NAME
+    add_concurrent_foreign_key :ci_builds, :ci_resource_groups, column: :resource_group_id, on_delete: :nullify
+  end
+
+  def down
+    remove_foreign_key_if_exists :ci_builds, column: :resource_group_id
+    remove_concurrent_index_by_name :ci_builds, INDEX_NAME
+  end
+end
diff --git a/db/schema.rb b/db/schema.rb
index deebbcb430df548bc365b94f105acab548dc7458..578961420c7cbf9ef5b0f8c1edcf905cb34d9f0a 100644
--- a/db/schema.rb
+++ b/db/schema.rb
@@ -683,6 +683,8 @@
     t.datetime_with_timezone "scheduled_at"
     t.string "token_encrypted"
     t.integer "upstream_pipeline_id"
+    t.bigint "resource_group_id"
+    t.datetime_with_timezone "waiting_for_resource_at"
     t.index ["artifacts_expire_at"], name: "index_ci_builds_on_artifacts_expire_at", where: "(artifacts_file <> ''::text)"
     t.index ["auto_canceled_by_id"], name: "index_ci_builds_on_auto_canceled_by_id"
     t.index ["commit_id", "artifacts_expire_at", "id"], name: "index_ci_builds_on_commit_id_and_artifacts_expireatandidpartial", where: "(((type)::text = 'Ci::Build'::text) AND ((retried = false) OR (retried IS NULL)) AND ((name)::text = ANY (ARRAY[('sast'::character varying)::text, ('dependency_scanning'::character varying)::text, ('sast:container'::character varying)::text, ('container_scanning'::character varying)::text, ('dast'::character varying)::text])))"
@@ -696,6 +698,7 @@
     t.index ["project_id"], name: "index_ci_builds_on_project_id_for_successfull_pages_deploy", where: "(((type)::text = 'GenericCommitStatus'::text) AND ((stage)::text = 'deploy'::text) AND ((name)::text = 'pages:deploy'::text) AND ((status)::text = 'success'::text))"
     t.index ["protected"], name: "index_ci_builds_on_protected"
     t.index ["queued_at"], name: "index_ci_builds_on_queued_at"
+    t.index ["resource_group_id", "id"], name: "index_for_resource_group", where: "(resource_group_id IS NOT NULL)"
     t.index ["runner_id"], name: "index_ci_builds_on_runner_id"
     t.index ["scheduled_at"], name: "partial_index_ci_builds_on_scheduled_at_with_scheduled_jobs", where: "((scheduled_at IS NOT NULL) AND ((type)::text = 'Ci::Build'::text) AND ((status)::text = 'scheduled'::text))"
     t.index ["stage_id", "stage_idx"], name: "tmp_build_stage_position_index", where: "(stage_idx IS NOT NULL)"
@@ -870,6 +873,23 @@
     t.index ["user_id"], name: "index_ci_pipelines_on_user_id"
   end
 
+  create_table "ci_resource_groups", force: :cascade do |t|
+    t.datetime_with_timezone "created_at", null: false
+    t.datetime_with_timezone "updated_at", null: false
+    t.bigint "project_id", null: false
+    t.string "key", limit: 255, null: false
+    t.index ["project_id", "key"], name: "index_ci_resource_groups_on_project_id_and_key", unique: true
+  end
+
+  create_table "ci_resources", force: :cascade do |t|
+    t.datetime_with_timezone "created_at", null: false
+    t.datetime_with_timezone "updated_at", null: false
+    t.bigint "resource_group_id", null: false
+    t.bigint "build_id"
+    t.index ["build_id"], name: "index_ci_resources_on_build_id"
+    t.index ["resource_group_id", "build_id"], name: "index_ci_resources_on_resource_group_id_and_build_id", unique: true
+  end
+
   create_table "ci_runner_namespaces", id: :serial, force: :cascade do |t|
     t.integer "runner_id"
     t.integer "namespace_id"
@@ -4360,6 +4380,7 @@
   add_foreign_key "ci_builds", "ci_pipelines", column: "auto_canceled_by_id", name: "fk_a2141b1522", on_delete: :nullify
   add_foreign_key "ci_builds", "ci_pipelines", column: "commit_id", name: "fk_d3130c9a7f", on_delete: :cascade
   add_foreign_key "ci_builds", "ci_pipelines", column: "upstream_pipeline_id", name: "fk_87f4cefcda", on_delete: :cascade
+  add_foreign_key "ci_builds", "ci_resource_groups", column: "resource_group_id", name: "fk_6661f4f0e8", on_delete: :nullify
   add_foreign_key "ci_builds", "ci_stages", column: "stage_id", name: "fk_3a9eaa254d", on_delete: :cascade
   add_foreign_key "ci_builds", "projects", name: "fk_befce0568a", on_delete: :cascade
   add_foreign_key "ci_builds_metadata", "ci_builds", column: "build_id", on_delete: :cascade
@@ -4380,6 +4401,9 @@
   add_foreign_key "ci_pipelines", "external_pull_requests", name: "fk_190998ef09", on_delete: :nullify
   add_foreign_key "ci_pipelines", "merge_requests", name: "fk_a23be95014", on_delete: :cascade
   add_foreign_key "ci_pipelines", "projects", name: "fk_86635dbd80", on_delete: :cascade
+  add_foreign_key "ci_resource_groups", "projects", on_delete: :cascade
+  add_foreign_key "ci_resources", "ci_builds", column: "build_id", on_delete: :nullify
+  add_foreign_key "ci_resources", "ci_resource_groups", column: "resource_group_id", on_delete: :cascade
   add_foreign_key "ci_runner_namespaces", "ci_runners", column: "runner_id", on_delete: :cascade
   add_foreign_key "ci_runner_namespaces", "namespaces", on_delete: :cascade
   add_foreign_key "ci_runner_projects", "projects", name: "fk_4478a6f1e4", on_delete: :cascade
diff --git a/lib/gitlab/ci/config/entry/job.rb b/lib/gitlab/ci/config/entry/job.rb
index eea59ecb937f31c5b2b38dffb3991382f1583462..860ceae2ab81a258f20fda762bea28fe0bf6c420 100644
--- a/lib/gitlab/ci/config/entry/job.rb
+++ b/lib/gitlab/ci/config/entry/job.rb
@@ -16,7 +16,8 @@ class Job < ::Gitlab::Config::Entry::Node
           ALLOWED_KEYS = %i[tags script only except rules type image services
                             allow_failure type stage when start_in artifacts cache
                             dependencies before_script needs after_script variables
-                            environment coverage retry parallel extends interruptible timeout].freeze
+                            environment coverage retry parallel extends interruptible timeout
+                            resource_group].freeze
 
           REQUIRED_BY_NEEDS = %i[stage].freeze
 
@@ -48,6 +49,7 @@ class Job < ::Gitlab::Config::Entry::Node
               validates :dependencies, array_of_strings: true
               validates :extends, array_of_strings_or_string: true
               validates :rules, array_of_hashes: true
+              validates :resource_group, type: String
             end
 
             validates :start_in, duration: { limit: '1 week' }, if: :delayed?
@@ -156,7 +158,7 @@ class Job < ::Gitlab::Config::Entry::Node
 
           attributes :script, :tags, :allow_failure, :when, :dependencies,
                      :needs, :retry, :parallel, :extends, :start_in, :rules,
-                     :interruptible, :timeout
+                     :interruptible, :timeout, :resource_group
 
           def self.matching?(name, config)
             !name.to_s.start_with?('.') &&
@@ -236,7 +238,8 @@ def to_hash
               artifacts: artifacts_value,
               after_script: after_script_value,
               ignore: ignored?,
-              needs: needs_defined? ? needs_value : nil }
+              needs: needs_defined? ? needs_value : nil,
+              resource_group: resource_group }
           end
         end
       end
diff --git a/lib/gitlab/ci/pipeline/seed/build.rb b/lib/gitlab/ci/pipeline/seed/build.rb
index 590c7f4d1ddbfddc5ad81305842a418668efe391..98b4b4593e0fb94ec6d1efec01c6ded77d76cae3 100644
--- a/lib/gitlab/ci/pipeline/seed/build.rb
+++ b/lib/gitlab/ci/pipeline/seed/build.rb
@@ -18,6 +18,7 @@ def initialize(pipeline, attributes, previous_stages)
             @seed_attributes = attributes
             @previous_stages = previous_stages
             @needs_attributes = dig(:needs_attributes)
+            @resource_group_key = attributes.delete(:resource_group_key)
 
             @using_rules  = attributes.key?(:rules)
             @using_only   = attributes.key?(:only)
@@ -78,6 +79,7 @@ def to_resource
               else
                 ::Ci::Build.new(attributes).tap do |job|
                   job.deployment = Seed::Deployment.new(job).to_resource
+                  job.resource_group = Seed::Build::ResourceGroup.new(job, @resource_group_key).to_resource
                 end
               end
             end
diff --git a/lib/gitlab/ci/pipeline/seed/build/resource_group.rb b/lib/gitlab/ci/pipeline/seed/build/resource_group.rb
new file mode 100644
index 0000000000000000000000000000000000000000..100eb1d4084d452d1f3ec39ffcac327061723162
--- /dev/null
+++ b/lib/gitlab/ci/pipeline/seed/build/resource_group.rb
@@ -0,0 +1,40 @@
+# frozen_string_literal: true
+
+module Gitlab
+  module Ci
+    module Pipeline
+      module Seed
+        class Build
+          class ResourceGroup < Seed::Base
+            include Gitlab::Utils::StrongMemoize
+
+            attr_reader :build, :resource_group_key
+
+            def initialize(build, resource_group_key)
+              @build = build
+              @resource_group_key = resource_group_key
+            end
+
+            def to_resource
+              return unless Feature.enabled?(:ci_resource_group, build.project)
+              return unless resource_group_key.present?
+
+              resource_group = build.project.resource_groups
+                .safe_find_or_create_by(key: expanded_resource_group_key)
+
+              resource_group if resource_group.persisted?
+            end
+
+            private
+
+            def expanded_resource_group_key
+              strong_memoize(:expanded_resource_group_key) do
+                ExpandVariables.expand(resource_group_key, -> { build.simple_variables })
+              end
+            end
+          end
+        end
+      end
+    end
+  end
+end
diff --git a/lib/gitlab/ci/yaml_processor.rb b/lib/gitlab/ci/yaml_processor.rb
index 833c545fc5b1313bf1b6ff895ee36458a49b54f7..6f1ab79064ad80a048675ff493fe1bc8cecbefde 100644
--- a/lib/gitlab/ci/yaml_processor.rb
+++ b/lib/gitlab/ci/yaml_processor.rb
@@ -44,6 +44,7 @@ def build_attributes(name)
           interruptible: job[:interruptible],
           rules: job[:rules],
           cache: job[:cache],
+          resource_group_key: job[:resource_group],
           options: {
             image: job[:image],
             services: job[:services],
diff --git a/lib/gitlab/import_export/import_export.yml b/lib/gitlab/import_export/import_export.yml
index 2fd4f18b7560fbe063b7d06b8142d11ae85900a4..f822e931bdbbfb4ad7adde0053bf56beb59c2bfc 100644
--- a/lib/gitlab/import_export/import_export.yml
+++ b/lib/gitlab/import_export/import_export.yml
@@ -203,6 +203,8 @@ excluded_attributes:
     - :artifacts_metadata_store
     - :artifacts_size
     - :commands
+    - :resource_group_id
+    - :waiting_for_resource_at
   push_event_payload:
     - :event_id
   project_badges:
diff --git a/spec/factories/ci/builds.rb b/spec/factories/ci/builds.rb
index ecb1f1996d9f9fdd5673ef0edfe9551367a4fef5..a38935c89ba1549af5b03d88e3f96d51c7a2e060 100644
--- a/spec/factories/ci/builds.rb
+++ b/spec/factories/ci/builds.rb
@@ -207,6 +207,14 @@
       trigger_request factory: :ci_trigger_request
     end
 
+    trait :resource_group do
+      waiting_for_resource_at { 5.minutes.ago }
+
+      after(:build) do |build, evaluator|
+        build.resource_group = create(:ci_resource_group, project: build.project)
+      end
+    end
+
     after(:build) do |build, evaluator|
       build.project ||= build.pipeline.project
     end
diff --git a/spec/factories/ci/resource.rb b/spec/factories/ci/resource.rb
new file mode 100644
index 0000000000000000000000000000000000000000..d47b3ba46352700dccbee7f85d37015307e82464
--- /dev/null
+++ b/spec/factories/ci/resource.rb
@@ -0,0 +1,11 @@
+# frozen_string_literal: true
+
+FactoryBot.define do
+  factory :ci_resource, class: Ci::Resource do
+    resource_group factory: :ci_resource_group
+
+    trait(:retained) do
+      build factory: :ci_build
+    end
+  end
+end
diff --git a/spec/factories/ci/resource_group.rb b/spec/factories/ci/resource_group.rb
new file mode 100644
index 0000000000000000000000000000000000000000..bdfc0740a456ff2e7fe1345049e6c068beb4f066
--- /dev/null
+++ b/spec/factories/ci/resource_group.rb
@@ -0,0 +1,8 @@
+# frozen_string_literal: true
+
+FactoryBot.define do
+  factory :ci_resource_group, class: Ci::ResourceGroup do
+    project
+    sequence(:key) { |n| "IOS_#{n}" }
+  end
+end
diff --git a/spec/lib/gitlab/ci/pipeline/seed/build/resource_group_spec.rb b/spec/lib/gitlab/ci/pipeline/seed/build/resource_group_spec.rb
new file mode 100644
index 0000000000000000000000000000000000000000..bf6985156d3680192b5a3dea1ae2df2a2445926b
--- /dev/null
+++ b/spec/lib/gitlab/ci/pipeline/seed/build/resource_group_spec.rb
@@ -0,0 +1,46 @@
+# frozen_string_literal: true
+
+require 'spec_helper'
+
+describe Gitlab::Ci::Pipeline::Seed::Build::ResourceGroup do
+  let_it_be(:project) { create(:project) }
+  let(:job) { build(:ci_build, project: project) }
+  let(:seed) { described_class.new(job, resource_group_key) }
+
+  describe '#to_resource' do
+    subject { seed.to_resource }
+
+    context 'when resource group key is specified' do
+      let(:resource_group_key) { 'iOS' }
+
+      it 'returns a resource group object' do
+        is_expected.to be_a(Ci::ResourceGroup)
+        expect(subject.key).to eq('iOS')
+      end
+
+      context 'when environment has an invalid URL' do
+        let(:resource_group_key) { ':::' }
+
+        it 'returns nothing' do
+          is_expected.to be_nil
+        end
+      end
+
+      context 'when there is a resource group already' do
+        let!(:resource_group) { create(:ci_resource_group, project: project, key: 'iOS') }
+
+        it 'does not create a new resource group' do
+          expect { subject }.not_to change { Ci::ResourceGroup.count }
+        end
+      end
+    end
+
+    context 'when resource group key is nil' do
+      let(:resource_group_key) { nil }
+
+      it 'returns nothing' do
+        is_expected.to be_nil
+      end
+    end
+  end
+end
diff --git a/spec/lib/gitlab/ci/pipeline/seed/build_spec.rb b/spec/lib/gitlab/ci/pipeline/seed/build_spec.rb
index 2ae513aea1b5154ea3638bad9c09ab86daca544c..5526ec9e16f877df9c1acae8599e11264b08e610 100644
--- a/spec/lib/gitlab/ci/pipeline/seed/build_spec.rb
+++ b/spec/lib/gitlab/ci/pipeline/seed/build_spec.rb
@@ -231,6 +231,15 @@
           end
         end
       end
+
+      context 'when job belongs to a resource group' do
+        let(:attributes) { { name: 'rspec', ref: 'master', resource_group_key: 'iOS' } }
+
+        it 'returns a job with resource group' do
+          expect(subject.resource_group).not_to be_nil
+          expect(subject.resource_group.key).to eq('iOS')
+        end
+      end
     end
 
     context 'when job is a bridge' do
diff --git a/spec/lib/gitlab/ci/yaml_processor_spec.rb b/spec/lib/gitlab/ci/yaml_processor_spec.rb
index ff8849f84d5ea6fa3ab44ae2ce2478791a38891c..fc57341b5bc38307b862b2d2a308b276632b19fa 100644
--- a/spec/lib/gitlab/ci/yaml_processor_spec.rb
+++ b/spec/lib/gitlab/ci/yaml_processor_spec.rb
@@ -239,6 +239,21 @@ module Ci
             end
           end
         end
+
+        describe 'resource group' do
+          context 'when resource group is defined' do
+            let(:config) do
+              YAML.dump(rspec: {
+                script:   'test',
+                resource_group: 'iOS'
+              })
+            end
+
+            it 'has the attributes' do
+              expect(subject[:resource_group_key]).to eq 'iOS'
+            end
+          end
+        end
       end
 
       describe '#stages_attributes' do
diff --git a/spec/lib/gitlab/import_export/all_models.yml b/spec/lib/gitlab/import_export/all_models.yml
index 8d436fb28e0ad690c4f46027ce1e58d27dae1e85..16fe5f23d14361c3165279d2426ab40fd8db8805 100644
--- a/spec/lib/gitlab/import_export/all_models.yml
+++ b/spec/lib/gitlab/import_export/all_models.yml
@@ -444,6 +444,7 @@ project:
 - service_desk_setting
 - import_failures
 - container_expiration_policy
+- resource_groups
 award_emoji:
 - awardable
 - user
diff --git a/spec/models/ci/build_spec.rb b/spec/models/ci/build_spec.rb
index acc54338a104e15b8539d24b67c5b04af55eddd3..bcab621ab6ab79cf919fbc8bc421e33c17543ff0 100644
--- a/spec/models/ci/build_spec.rb
+++ b/spec/models/ci/build_spec.rb
@@ -1275,6 +1275,68 @@
       end
     end
 
+    describe '#requires_resource?' do
+      subject { build.requires_resource? }
+
+      context 'when build needs a resource from a resource group' do
+        let(:resource_group) { create(:ci_resource_group, project: project) }
+        let(:build) { create(:ci_build, resource_group: resource_group, project: project) }
+
+        context 'when build has not retained a resource' do
+          it { is_expected.to eq(true) }
+        end
+
+        context 'when build has retained a resource' do
+          before do
+            resource_group.retain_resource_for(build)
+          end
+
+          it { is_expected.to eq(false) }
+
+          context 'when ci_resource_group feature flag is disabled' do
+            before do
+              stub_feature_flags(ci_resource_group: false)
+            end
+
+            it { is_expected.to eq(false) }
+          end
+        end
+      end
+
+      context 'when build does not need a resource from a resource group' do
+        let(:build) { create(:ci_build, project: project) }
+
+        it { is_expected.to eq(false) }
+      end
+    end
+
+    describe '#retains_resource?' do
+      subject { build.retains_resource? }
+
+      context 'when build needs a resource from a resource group' do
+        let(:resource_group) { create(:ci_resource_group, project: project) }
+        let(:build) { create(:ci_build, resource_group: resource_group, project: project) }
+
+        context 'when build has retained a resource' do
+          before do
+            resource_group.retain_resource_for(build)
+          end
+
+          it { is_expected.to eq(true) }
+        end
+
+        context 'when build has not retained a resource' do
+          it { is_expected.to eq(false) }
+        end
+      end
+
+      context 'when build does not need a resource from a resource group' do
+        let(:build) { create(:ci_build, project: project) }
+
+        it { is_expected.to eq(false) }
+      end
+    end
+
     describe '#stops_environment?' do
       subject { build.stops_environment? }
 
diff --git a/spec/models/ci/resource_group_spec.rb b/spec/models/ci/resource_group_spec.rb
new file mode 100644
index 0000000000000000000000000000000000000000..213a57c2d7831f54a031ce4d2c2422899dc1a128
--- /dev/null
+++ b/spec/models/ci/resource_group_spec.rb
@@ -0,0 +1,88 @@
+# frozen_string_literal: true
+
+require 'spec_helper'
+
+describe Ci::ResourceGroup do
+  describe 'validation' do
+    it 'valids when key includes allowed character' do
+      resource_group = build(:ci_resource_group, key: 'test')
+
+      expect(resource_group).to be_valid
+    end
+
+    it 'invalids when key includes invalid character' do
+      resource_group = build(:ci_resource_group, key: ':::')
+
+      expect(resource_group).not_to be_valid
+    end
+  end
+
+  describe '#ensure_resource' do
+    it 'creates one resource when resource group is created' do
+      resource_group = create(:ci_resource_group)
+
+      expect(resource_group.resources.count).to eq(1)
+      expect(resource_group.resources.all?(&:persisted?)).to eq(true)
+    end
+  end
+
+  describe '#retain_resource_for' do
+    subject { resource_group.retain_resource_for(build) }
+
+    let(:build) { create(:ci_build) }
+    let(:resource_group) { create(:ci_resource_group) }
+
+    it 'retains resource for the build' do
+      expect(resource_group.resources.first.build).to be_nil
+
+      is_expected.to eq(true)
+
+      expect(resource_group.resources.first.build).to eq(build)
+    end
+
+    context 'when there are no free resources' do
+      before do
+        resource_group.retain_resource_for(create(:ci_build))
+      end
+
+      it 'fails to retain resource' do
+        is_expected.to eq(false)
+      end
+    end
+
+    context 'when the build has already retained a resource' do
+      let!(:another_resource) { create(:ci_resource, resource_group: resource_group, build: build) }
+
+      it 'fails to retain resource' do
+        expect { subject }.to raise_error(ActiveRecord::RecordNotUnique)
+      end
+    end
+  end
+
+  describe '#release_resource_from' do
+    subject { resource_group.release_resource_from(build) }
+
+    let(:build) { create(:ci_build) }
+    let(:resource_group) { create(:ci_resource_group) }
+
+    context 'when the build has already retained a resource' do
+      before do
+        resource_group.retain_resource_for(build)
+      end
+
+      it 'releases resource from the build' do
+        expect(resource_group.resources.first.build).to eq(build)
+
+        is_expected.to eq(true)
+
+        expect(resource_group.resources.first.build).to be_nil
+      end
+    end
+
+    context 'when the build has already released a resource' do
+      it 'fails to release resource' do
+        is_expected.to eq(false)
+      end
+    end
+  end
+end
diff --git a/spec/models/ci/resource_spec.rb b/spec/models/ci/resource_spec.rb
new file mode 100644
index 0000000000000000000000000000000000000000..27e512e2c454b7811c0a90d434328b513c84a8d2
--- /dev/null
+++ b/spec/models/ci/resource_spec.rb
@@ -0,0 +1,28 @@
+# frozen_string_literal: true
+
+require 'spec_helper'
+
+describe Ci::Resource do
+  describe '.free' do
+    subject { described_class.free }
+
+    let(:resource_group) { create(:ci_resource_group) }
+    let!(:free_resource) { resource_group.resources.take }
+    let!(:retained_resource) { create(:ci_resource, :retained, resource_group: resource_group) }
+
+    it 'returns free resources' do
+      is_expected.to eq([free_resource])
+    end
+  end
+
+  describe '.retained_by' do
+    subject { described_class.retained_by(build) }
+
+    let(:build) { create(:ci_build) }
+    let!(:resource) { create(:ci_resource, build: build) }
+
+    it 'returns retained resources' do
+      is_expected.to eq([resource])
+    end
+  end
+end
diff --git a/spec/services/ci/create_pipeline_service_spec.rb b/spec/services/ci/create_pipeline_service_spec.rb
index 3d2d8691c687508a86d344829dbfb7a2329fa87b..4c83f9229d99fb0d69232264a5dbeee7c685ec9d 100644
--- a/spec/services/ci/create_pipeline_service_spec.rb
+++ b/spec/services/ci/create_pipeline_service_spec.rb
@@ -914,6 +914,44 @@ def previous_commit_sha_from_ref(ref)
       end
     end
 
+    context 'with resource group' do
+      context 'when resource group is defined' do
+        before do
+          config = YAML.dump(
+            test: { stage: 'test', script: 'ls', resource_group: resource_group_key }
+          )
+
+          stub_ci_pipeline_yaml_file(config)
+        end
+
+        let(:resource_group_key) { 'iOS' }
+
+        it 'persists the association correctly' do
+          result = execute_service
+          deploy_job = result.builds.find_by_name!(:test)
+          resource_group = project.resource_groups.find_by_key!(resource_group_key)
+
+          expect(result).to be_persisted
+          expect(deploy_job.resource_group.key).to eq(resource_group_key)
+          expect(project.resource_groups.count).to eq(1)
+          expect(resource_group.builds.count).to eq(1)
+          expect(resource_group.resources.count).to eq(1)
+          expect(resource_group.resources.first.build).to eq(nil)
+        end
+
+        context 'when resourc group key includes predefined variables' do
+          let(:resource_group_key) { '$CI_COMMIT_REF_NAME-$CI_JOB_NAME' }
+
+          it 'interpolates the variables into the key correctly' do
+            result = execute_service
+
+            expect(result).to be_persisted
+            expect(project.resource_groups.exists?(key: 'master-test')).to eq(true)
+          end
+        end
+      end
+    end
+
     context 'with timeout' do
       context 'when builds with custom timeouts are configured' do
         before do
diff --git a/spec/services/ci/retry_build_service_spec.rb b/spec/services/ci/retry_build_service_spec.rb
index b1368f7776ba968dd1384017591c42f9ffec5960..76fe6f53a1197db19d9b082eb832e8facaa922b7 100644
--- a/spec/services/ci/retry_build_service_spec.rb
+++ b/spec/services/ci/retry_build_service_spec.rb
@@ -31,7 +31,7 @@
        job_artifacts_container_scanning job_artifacts_dast
        job_artifacts_license_management job_artifacts_performance
        job_artifacts_codequality job_artifacts_metrics scheduled_at
-       job_variables].freeze
+       job_variables waiting_for_resource_at].freeze
 
   IGNORE_ACCESSORS =
     %i[type lock_version target_url base_tags trace_sections
@@ -40,14 +40,14 @@
        user_id auto_canceled_by_id retried failure_reason
        sourced_pipelines artifacts_file_store artifacts_metadata_store
        metadata runner_session trace_chunks upstream_pipeline_id
-       artifacts_file artifacts_metadata artifacts_size commands].freeze
+       artifacts_file artifacts_metadata artifacts_size commands resource resource_group_id].freeze
 
   shared_examples 'build duplication' do
     let(:another_pipeline) { create(:ci_empty_pipeline, project: project) }
 
     let(:build) do
       create(:ci_build, :failed, :expired, :erased, :queued, :coverage, :tags,
-             :allowed_to_fail, :on_tag, :triggered, :teardown_environment,
+             :allowed_to_fail, :on_tag, :triggered, :teardown_environment, :resource_group,
              description: 'my-job', stage: 'test', stage_id: stage.id,
              pipeline: pipeline, auto_canceled_by: another_pipeline,
              scheduled_at: 10.seconds.since)