diff --git a/CHANGELOG b/CHANGELOG
index 5ff0cb42ccc3db6af0c74b046cf69ff0e6f9834b..fb38db156308d45fa9596eb975fd1946e21b9001 100644
--- a/CHANGELOG
+++ b/CHANGELOG
@@ -5,6 +5,7 @@ v 8.11.0 (unreleased)
   - Fix CI status icon link underline (ClemMakesApps)
   - Fix of 'Commits being passed to custom hooks are already reachable when using the UI'
   - Add support for using RequestStore within Sidekiq tasks via SIDEKIQ_REQUEST_STORE env variable
+  - Optimize maximum user access level lookup in loading of notes
   - Limit git rev-list output count to one in forced push check
   - Add green outline to New Branch button. !5447 (winniehell)
   - Retrieve rendered HTML from cache in one request
diff --git a/app/controllers/projects/issues_controller.rb b/app/controllers/projects/issues_controller.rb
index fa663c9bda4f0e24ca5133bdbca33a1cbe7ae395..16ed7c2b6b4d17d9e49a7289d77e84ee67c33a1b 100644
--- a/app/controllers/projects/issues_controller.rb
+++ b/app/controllers/projects/issues_controller.rb
@@ -1,4 +1,5 @@
 class Projects::IssuesController < Projects::ApplicationController
+  include NotesHelper
   include ToggleSubscriptionAction
   include IssuableActions
   include ToggleAwardEmoji
@@ -70,6 +71,8 @@ class Projects::IssuesController < Projects::ApplicationController
     @note     = @project.notes.new(noteable: @issue)
     @noteable = @issue
 
+    preload_max_access_for_authors(@notes, @project) if @notes
+
     respond_to do |format|
       format.html
       format.json do
diff --git a/app/controllers/projects/merge_requests_controller.rb b/app/controllers/projects/merge_requests_controller.rb
index 594a61464b9aecf7c9b186a7c83fb3f9a6c40efc..da1b9c3e48a485cdfbfcc36070ab3488da6002b0 100644
--- a/app/controllers/projects/merge_requests_controller.rb
+++ b/app/controllers/projects/merge_requests_controller.rb
@@ -3,6 +3,7 @@ class Projects::MergeRequestsController < Projects::ApplicationController
   include DiffForPath
   include DiffHelper
   include IssuableActions
+  include NotesHelper
   include ToggleAwardEmoji
 
   before_action :module_enabled
@@ -385,6 +386,8 @@ class Projects::MergeRequestsController < Projects::ApplicationController
       @project_wiki,
       @ref
     )
+
+    preload_max_access_for_authors(@notes, @project) if @notes
   end
 
   def define_widget_vars
diff --git a/app/helpers/notes_helper.rb b/app/helpers/notes_helper.rb
index 0f60dd828abe52e51da89504ac3adf4536a33f7e..0c47abe0fbad45987c509358ee9cca70db463af8 100644
--- a/app/helpers/notes_helper.rb
+++ b/app/helpers/notes_helper.rb
@@ -7,7 +7,7 @@ module NotesHelper
   end
 
   def note_editable?(note)
-    note.editable? && can?(current_user, :admin_note, note)
+    Ability.can_edit_note?(current_user, note)
   end
 
   def noteable_json(noteable)
@@ -87,14 +87,13 @@ module NotesHelper
     end
   end
 
-  def note_max_access_for_user(note)
-    @max_access_by_user_id ||= Hash.new do |hash, key|
-      project = key[:project]
-      hash[key] = project.team.human_max_access(key[:user_id])
-    end
+  def preload_max_access_for_authors(notes, project)
+    user_ids = notes.map(&:author_id)
+    project.team.max_member_access_for_user_ids(user_ids)
+  end
 
-    full_key = { project: note.project, user_id: note.author_id }
-    @max_access_by_user_id[full_key]
+  def note_max_access_for_user(note)
+    note.project.team.human_max_access(note.author_id)
   end
 
   def discussion_diff_path(discussion)
diff --git a/app/models/ability.rb b/app/models/ability.rb
index f33c8d61d3fedb39750ddfc3548379ada813f87e..6884d99c5a6493e66fd5591ca6123713f30e60c1 100644
--- a/app/models/ability.rb
+++ b/app/models/ability.rb
@@ -388,6 +388,20 @@ class Ability
       GroupProjectsFinder.new(group).execute(user).any?
     end
 
+    def can_edit_note?(user, note)
+      return false unless note.editable?
+      return false unless user.present?
+      return true if note.author == user
+      return true if user.admin?
+
+      if note.project
+        max_access_level = note.project.team.max_member_access(user.id)
+        max_access_level >= Gitlab::Access::MASTER
+      else
+        false
+      end
+    end
+
     def namespace_abilities(user, namespace)
       rules = []
 
diff --git a/app/models/project_team.rb b/app/models/project_team.rb
index 9d312a53790528cc613e02f54912017f3726d235..67faea1f9f3e10d07bdcf1cef84bc0bac0b861f8 100644
--- a/app/models/project_team.rb
+++ b/app/models/project_team.rb
@@ -132,22 +132,41 @@ class ProjectTeam
     Gitlab::Access.options_with_owner.key(max_member_access(user_id))
   end
 
-  # This method assumes project and group members are eager loaded for optimal
-  # performance.
-  def max_member_access(user_id)
-    access = []
+  # Determine the maximum access level for a group of users in bulk.
+  #
+  # Returns a Hash mapping user ID -> maxmum access level.
+  def max_member_access_for_user_ids(user_ids)
+    user_ids = user_ids.uniq
+    key = "max_member_access:#{project.id}"
+    RequestStore.store[key] ||= Hash.new
+    access = RequestStore.store[key]
 
-    access += project.members.where(user_id: user_id).has_access.pluck(:access_level)
+    # Lookup only the IDs we need
+    user_ids = user_ids - access.keys
 
-    if group
-      access += group.members.where(user_id: user_id).has_access.pluck(:access_level)
-    end
+    if user_ids.present?
+      user_ids.map { |id| access[id] = Gitlab::Access::NO_ACCESS }
 
-    if project.invited_groups.any? && project.allowed_to_share_with_group?
-      access << max_invited_level(user_id)
+      member_access = project.members.where(user_id: user_ids).has_access.pluck(:user_id, :access_level).to_h
+      merge_max!(access, member_access)
+
+      if group
+        group_access = group.members.where(user_id: user_ids).has_access.pluck(:user_id, :access_level).to_h
+        merge_max!(access, group_access)
+      end
+
+      if project.invited_groups.any? && project.allowed_to_share_with_group?
+        # Not optimized
+        invited_levels = user_ids.map { |id| [id, max_invited_level(id)] }.to_h
+        merge_max!(access, invited_levels)
+      end
     end
 
-    access.compact.max
+    access
+  end
+
+  def max_member_access(user_id)
+    max_member_access_for_user_ids([user_id])[user_id]
   end
 
   private
@@ -156,6 +175,7 @@ class ProjectTeam
     project.project_group_links.map do |group_link|
       invited_group = group_link.group
       access = invited_group.group_members.find_by(user_id: user_id).try(:access_field)
+      access = Gitlab::Access::NO_ACCESS unless access.present?
 
       # If group member has higher access level we should restrict it
       # to max allowed access level
@@ -215,4 +235,8 @@ class ProjectTeam
   def group
     project.group
   end
+
+  def merge_max!(first_hash, second_hash)
+    first_hash.merge!(second_hash) { |_key, old, new| old > new ? old : new }
+  end
 end
diff --git a/lib/gitlab/access.rb b/lib/gitlab/access.rb
index de41ea415a67d17ab461dde421c7a6fc551d7649..a533bac26925ff589a89a4c312df8040769e28bd 100644
--- a/lib/gitlab/access.rb
+++ b/lib/gitlab/access.rb
@@ -7,6 +7,7 @@ module Gitlab
   module Access
     class AccessDeniedError < StandardError; end
 
+    NO_ACCESS = 0
     GUEST     = 10
     REPORTER  = 20
     DEVELOPER = 30
diff --git a/spec/helpers/notes_helper_spec.rb b/spec/helpers/notes_helper_spec.rb
index 08a9350325872fb451a6657f9791ba41ba4826c5..af371248ae95ee943a14fa2b377ea368d8dbd1a4 100644
--- a/spec/helpers/notes_helper_spec.rb
+++ b/spec/helpers/notes_helper_spec.rb
@@ -1,37 +1,30 @@
 require "spec_helper"
 
 describe NotesHelper do
-  describe "#notes_max_access_for_users" do
-    let(:owner) { create(:owner) }
-    let(:group) { create(:group) }
-    let(:project) { create(:empty_project, namespace: group) }
-    let(:master) { create(:user) }
-    let(:reporter) { create(:user) }
-    let(:guest) { create(:user) }
-
-    let(:owner_note) { create(:note, author: owner, project: project) }
-    let(:master_note) { create(:note, author: master, project: project) }
-    let(:reporter_note) { create(:note, author: reporter, project: project) }
-    let!(:notes) { [owner_note, master_note, reporter_note] }
-
-    before do
-      group.add_owner(owner)
-      project.team << [master, :master]
-      project.team << [reporter, :reporter]
-      project.team << [guest, :guest]
-    end
+  let(:owner) { create(:owner) }
+  let(:group) { create(:group) }
+  let(:project) { create(:empty_project, namespace: group) }
+  let(:master) { create(:user) }
+  let(:reporter) { create(:user) }
+  let(:guest) { create(:user) }
 
-    it 'return human access levels' do
-      original_method = project.team.method(:human_max_access)
-      expect_any_instance_of(ProjectTeam).to receive(:human_max_access).exactly(3).times do |*args|
-        original_method.call(args[1])
-      end
+  let(:owner_note) { create(:note, author: owner, project: project) }
+  let(:master_note) { create(:note, author: master, project: project) }
+  let(:reporter_note) { create(:note, author: reporter, project: project) }
+  let!(:notes) { [owner_note, master_note, reporter_note] }
 
+  before do
+    group.add_owner(owner)
+    project.team << [master, :master]
+    project.team << [reporter, :reporter]
+    project.team << [guest, :guest]
+  end
+
+  describe "#notes_max_access_for_users" do
+    it 'return human access levels' do
       expect(helper.note_max_access_for_user(owner_note)).to eq('Owner')
       expect(helper.note_max_access_for_user(master_note)).to eq('Master')
       expect(helper.note_max_access_for_user(reporter_note)).to eq('Reporter')
-      # Call it again to ensure value is cached
-      expect(helper.note_max_access_for_user(owner_note)).to eq('Owner')
     end
 
     it 'handles access in different projects' do
@@ -43,4 +36,16 @@ describe NotesHelper do
       expect(helper.note_max_access_for_user(other_note)).to eq('Reporter')
     end
   end
+
+  describe '#preload_max_access_for_authors' do
+    it 'loads multiple users' do
+      expected_access = {
+        owner.id => Gitlab::Access::OWNER,
+        master.id => Gitlab::Access::MASTER,
+        reporter.id => Gitlab::Access::REPORTER
+      }
+
+      expect(helper.preload_max_access_for_authors(notes, project)).to eq(expected_access)
+    end
+  end
 end
diff --git a/spec/models/ability_spec.rb b/spec/models/ability_spec.rb
index 1acb5846fcf9028026ddb5104637bfb58fc791e7..cd5f40fe3d29fd826ce5597ceeba1bbd4d257e03 100644
--- a/spec/models/ability_spec.rb
+++ b/spec/models/ability_spec.rb
@@ -1,6 +1,62 @@
 require 'spec_helper'
 
 describe Ability, lib: true do
+  describe '.can_edit_note?' do
+    let(:project) { create(:empty_project) }
+    let!(:note) { create(:note_on_issue, project: project) }
+
+    context 'using an anonymous user' do
+      it 'returns false' do
+        expect(described_class.can_edit_note?(nil, note)).to be_falsy
+      end
+    end
+
+    context 'using a system note' do
+      it 'returns false' do
+        system_note = create(:note, system: true)
+        user = create(:user)
+
+        expect(described_class.can_edit_note?(user, system_note)).to be_falsy
+      end
+    end
+
+    context 'using users with different access levels' do
+      let(:user) { create(:user) }
+
+      it 'returns true for the author' do
+        expect(described_class.can_edit_note?(note.author, note)).to be_truthy
+      end
+
+      it 'returns false for a guest user' do
+        project.team << [user, :guest]
+
+        expect(described_class.can_edit_note?(user, note)).to be_falsy
+      end
+
+      it 'returns false for a developer' do
+        project.team << [user, :developer]
+
+        expect(described_class.can_edit_note?(user, note)).to be_falsy
+      end
+
+      it 'returns true for a master' do
+        project.team << [user, :master]
+
+        expect(described_class.can_edit_note?(user, note)).to be_truthy
+      end
+
+      it 'returns true for a group owner' do
+        group = create(:group)
+        project.project_group_links.create(
+          group: group,
+          group_access: Gitlab::Access::MASTER)
+        group.add_owner(user)
+
+        expect(described_class.can_edit_note?(user, note)).to be_truthy
+      end
+    end
+  end
+
   describe '.users_that_can_read_project' do
     context 'using a public project' do
       it 'returns all the users' do
diff --git a/spec/models/project_team_spec.rb b/spec/models/project_team_spec.rb
index 9262aeb6ed890a074f2971af20509474711e9b01..115fffd82d92eccefc6a3207bdbeb8aa74e58ac5 100644
--- a/spec/models/project_team_spec.rb
+++ b/spec/models/project_team_spec.rb
@@ -151,8 +151,8 @@ describe ProjectTeam, models: true do
         it { expect(project.team.max_member_access(master.id)).to eq(Gitlab::Access::MASTER) }
         it { expect(project.team.max_member_access(reporter.id)).to eq(Gitlab::Access::REPORTER) }
         it { expect(project.team.max_member_access(guest.id)).to eq(Gitlab::Access::GUEST) }
-        it { expect(project.team.max_member_access(nonmember.id)).to be_nil }
-        it { expect(project.team.max_member_access(requester.id)).to be_nil }
+        it { expect(project.team.max_member_access(nonmember.id)).to eq(Gitlab::Access::NO_ACCESS) }
+        it { expect(project.team.max_member_access(requester.id)).to eq(Gitlab::Access::NO_ACCESS) }
       end
 
       context 'when project is shared with group' do
@@ -168,14 +168,14 @@ describe ProjectTeam, models: true do
 
         it { expect(project.team.max_member_access(master.id)).to eq(Gitlab::Access::DEVELOPER) }
         it { expect(project.team.max_member_access(reporter.id)).to eq(Gitlab::Access::REPORTER) }
-        it { expect(project.team.max_member_access(nonmember.id)).to be_nil }
-        it { expect(project.team.max_member_access(requester.id)).to be_nil }
+        it { expect(project.team.max_member_access(nonmember.id)).to eq(Gitlab::Access::NO_ACCESS) }
+        it { expect(project.team.max_member_access(requester.id)).to eq(Gitlab::Access::NO_ACCESS) }
 
         context 'but share_with_group_lock is true' do
           before { project.namespace.update(share_with_group_lock: true) }
 
-          it { expect(project.team.max_member_access(master.id)).to be_nil }
-          it { expect(project.team.max_member_access(reporter.id)).to be_nil }
+          it { expect(project.team.max_member_access(master.id)).to eq(Gitlab::Access::NO_ACCESS) }
+          it { expect(project.team.max_member_access(reporter.id)).to eq(Gitlab::Access::NO_ACCESS) }
         end
       end
     end
@@ -194,8 +194,43 @@ describe ProjectTeam, models: true do
       it { expect(project.team.max_member_access(master.id)).to eq(Gitlab::Access::MASTER) }
       it { expect(project.team.max_member_access(reporter.id)).to eq(Gitlab::Access::REPORTER) }
       it { expect(project.team.max_member_access(guest.id)).to eq(Gitlab::Access::GUEST) }
-      it { expect(project.team.max_member_access(nonmember.id)).to be_nil }
-      it { expect(project.team.max_member_access(requester.id)).to be_nil }
+      it { expect(project.team.max_member_access(nonmember.id)).to eq(Gitlab::Access::NO_ACCESS) }
+      it { expect(project.team.max_member_access(requester.id)).to eq(Gitlab::Access::NO_ACCESS) }
+    end
+  end
+
+  describe "#max_member_access_for_users" do
+    it 'returns correct roles for different users' do
+      master = create(:user)
+      reporter = create(:user)
+      promoted_guest = create(:user)
+      guest = create(:user)
+      project = create(:project)
+
+      project.team << [master, :master]
+      project.team << [reporter, :reporter]
+      project.team << [promoted_guest, :guest]
+      project.team << [guest, :guest]
+
+      group = create(:group)
+      group_developer = create(:user)
+      project.project_group_links.create(
+        group: group,
+        group_access: Gitlab::Access::DEVELOPER)
+
+      group.add_master(promoted_guest)
+      group.add_developer(group_developer)
+      users = [master, reporter, promoted_guest, guest, group_developer].map(&:id)
+
+      expected = {
+          master.id => Gitlab::Access::MASTER,
+          reporter.id => Gitlab::Access::REPORTER,
+          promoted_guest.id => Gitlab::Access::DEVELOPER,
+          guest.id => Gitlab::Access::GUEST,
+          group_developer.id => Gitlab::Access::DEVELOPER
+      }
+
+      expect(project.team.max_member_access_for_user_ids(users)).to eq(expected)
     end
   end
 end