diff --git a/app/controllers/concerns/notes_actions.rb b/app/controllers/concerns/notes_actions.rb
index a57d9e6e6c0..14e755c8d97 100644
--- a/app/controllers/concerns/notes_actions.rb
+++ b/app/controllers/concerns/notes_actions.rb
@@ -11,14 +11,16 @@ module NotesActions
 
     notes_json = { notes: [], last_fetched_at: current_fetched_at }
 
-    @notes = notes_finder.execute.inc_relations_for_view
+    @notes = notes_finder.execute.inc_relations_for_view.to_a
+    @notes.reject! { |n| n.cross_reference_not_visible_for?(current_user) }
     @notes = prepare_notes_for_rendering(@notes)
 
-    @notes.each do |note|
-      next if note.cross_reference_not_visible_for?(current_user)
-
-      notes_json[:notes] << note_json(note)
-    end
+    notes_json[:notes] =
+      if params[:full_data]
+        note_serializer.represent(@notes)
+      else
+        @notes.map { |note| note_json(note) }
+      end
 
     render json: notes_json
   end
@@ -80,22 +82,27 @@ module NotesActions
     }
 
     if note.persisted?
-      attrs.merge!(
-        valid: true,
-        id: note.id,
-        discussion_id: note.discussion_id(noteable),
-        html: note_html(note),
-        note: note.note
-      )
+      attrs[:valid] = true
 
-      discussion = note.to_discussion(noteable)
-      unless discussion.individual_note?
+      if params[:full_data]
+        attrs.merge!(note_serializer.represent(note))
+      else
         attrs.merge!(
-          discussion_resolvable: discussion.resolvable?,
-
-          diff_discussion_html: diff_discussion_html(discussion),
-          discussion_html: discussion_html(discussion)
+          id: note.id,
+          discussion_id: note.discussion_id(noteable),
+          html: note_html(note),
+          note: note.note
         )
+
+        discussion = note.to_discussion(noteable)
+        unless discussion.individual_note?
+          attrs.merge!(
+            discussion_resolvable: discussion.resolvable?,
+
+            diff_discussion_html: diff_discussion_html(discussion),
+            discussion_html: discussion_html(discussion)
+          )
+        end
       end
     else
       attrs.merge!(
@@ -177,4 +184,8 @@ module NotesActions
   def notes_finder
     @notes_finder ||= NotesFinder.new(project, current_user, finder_params)
   end
+
+  def note_serializer
+    NoteSerializer.new(project: project, noteable: noteable, current_user: current_user)
+  end
 end
diff --git a/app/controllers/projects/issues_controller.rb b/app/controllers/projects/issues_controller.rb
index 0ac9da2ff0f..153c490ce3f 100644
--- a/app/controllers/projects/issues_controller.rb
+++ b/app/controllers/projects/issues_controller.rb
@@ -97,6 +97,14 @@ class Projects::IssuesController < Projects::ApplicationController
     end
   end
 
+  def discussions
+    @discussions = @issue.discussions
+    @discussions.reject! { |d| d.individual_note? && d.first_note.cross_reference_not_visible_for?(current_user) }
+    prepare_notes_for_rendering(@discussions.flat_map(&:notes))
+
+    render json: DiscussionSerializer.new(project: @project, noteable: @issue, current_user: current_user).represent(@discussions)
+  end
+
   def create
     create_params = issue_params.merge(spammable_params).merge(
       merge_request_to_resolve_discussions_of: params[:merge_request_to_resolve_discussions_of],
diff --git a/app/helpers/issues_helper.rb b/app/helpers/issues_helper.rb
index 42b6cfdf02f..034b4451b56 100644
--- a/app/helpers/issues_helper.rb
+++ b/app/helpers/issues_helper.rb
@@ -119,7 +119,7 @@ module IssuesHelper
   end
 
   def awards_sort(awards)
-    awards.sort_by do |award, notes|
+    awards.sort_by do |award, award_emojis|
       if award == "thumbsup"
         0
       elsif award == "thumbsdown"
diff --git a/app/helpers/system_note_helper.rb b/app/helpers/system_note_helper.rb
index 209bd56b78a..69366825124 100644
--- a/app/helpers/system_note_helper.rb
+++ b/app/helpers/system_note_helper.rb
@@ -21,8 +21,14 @@ module SystemNoteHelper
     'outdated' => 'icon_edit'
   }.freeze
 
+  def system_note_icon_name(note)
+    ICON_NAMES_BY_ACTION[note.system_note_metadata&.action]
+  end
+
   def icon_for_system_note(note)
-    icon_name = ICON_NAMES_BY_ACTION[note.system_note_metadata&.action]
+    icon_name = system_note_icon_name(note)
     custom_icon(icon_name) if icon_name
   end
+
+  extend self
 end
diff --git a/app/models/discussion.rb b/app/models/discussion.rb
index d1cec7613af..b80da7b246a 100644
--- a/app/models/discussion.rb
+++ b/app/models/discussion.rb
@@ -81,6 +81,10 @@ class Discussion
     last_note.author
   end
 
+  def updated?
+    last_updated_at != created_at
+  end
+
   def id
     first_note.discussion_id(context_noteable)
   end
diff --git a/app/serializers/award_emoji_entity.rb b/app/serializers/award_emoji_entity.rb
new file mode 100644
index 00000000000..6e03cd02392
--- /dev/null
+++ b/app/serializers/award_emoji_entity.rb
@@ -0,0 +1,4 @@
+class AwardEmojiEntity < Grape::Entity
+  expose :name
+  expose :user, using: API::Entities::UserSafe
+end
diff --git a/app/serializers/discussion_entity.rb b/app/serializers/discussion_entity.rb
new file mode 100644
index 00000000000..cb6c3c23807
--- /dev/null
+++ b/app/serializers/discussion_entity.rb
@@ -0,0 +1,20 @@
+class DiscussionEntity < Grape::Entity
+  include RequestAwareEntity
+
+  expose :id, :reply_id
+  expose :expanded?, as: :expanded
+  expose :author, using: UserEntity
+
+  expose :created_at
+
+  expose :last_updated_at, if: -> (discussion, _) { discussion.updated? }
+  expose :last_updated_by, if: -> (discussion, _) { discussion.updated? }, using: UserEntity
+
+  expose :notes, using: NoteEntity
+
+  expose :individual_note?, as: :individual_note
+
+  expose :can_reply do |discussion|
+    can?(request.current_user, :create_note, discussion.project)
+  end
+end
diff --git a/app/serializers/discussion_serializer.rb b/app/serializers/discussion_serializer.rb
new file mode 100644
index 00000000000..ed5e1224bb2
--- /dev/null
+++ b/app/serializers/discussion_serializer.rb
@@ -0,0 +1,3 @@
+class DiscussionSerializer < BaseSerializer
+  entity DiscussionEntity
+end
diff --git a/app/serializers/note_attachment_entity.rb b/app/serializers/note_attachment_entity.rb
new file mode 100644
index 00000000000..1ad50568ab9
--- /dev/null
+++ b/app/serializers/note_attachment_entity.rb
@@ -0,0 +1,5 @@
+class NoteAttachmentEntity < Grape::Entity
+  expose :url
+  expose :filename
+  expose :image?, as: :image
+end
diff --git a/app/serializers/note_entity.rb b/app/serializers/note_entity.rb
new file mode 100644
index 00000000000..7a49ec4ef55
--- /dev/null
+++ b/app/serializers/note_entity.rb
@@ -0,0 +1,58 @@
+class NoteEntity < API::Entities::Note
+  include RequestAwareEntity
+
+  expose :type
+
+  expose :author, using: UserEntity
+
+  expose :human_access do |note|
+    note.project.team.human_max_access(note.author_id)
+  end
+
+  unexpose :note, as: :body
+  expose :note
+
+  expose :redacted_note_html, as: :note_html
+
+  expose :last_edited_at, if: -> (note, _) { note.is_edited? }
+  expose :last_edited_by, using: UserEntity, if: -> (note, _) { note.is_edited? }
+
+  expose :can_edit do |note|
+    Ability.can_edit_note?(request.current_user, note)
+  end
+
+  expose :system_note_icon_name, if: -> (note, _) { note.system? } do |note|
+    SystemNoteHelper.system_note_icon_name(note)
+  end
+
+  expose :discussion_id do |note|
+    note.discussion_id(request.noteable)
+  end
+
+  expose :emoji_awardable?, as: :emoji_awardable
+  expose :award_emoji, if: -> (note, _) { note.emoji_awardable? }, using: AwardEmojiEntity
+  expose :toggle_award_path, if: -> (note, _) { note.emoji_awardable? } do |note|
+    if note.for_personal_snippet?
+      toggle_award_emoji_snippet_note_path(note.noteable, note)
+    else
+      toggle_award_emoji_namespace_project_note_path(note.project.namespace, note.project, note.id)
+    end
+  end
+
+  expose :report_abuse_path do |note|
+    new_abuse_report_path(user_id: note.author.id, ref_url: Gitlab::UrlBuilder.build(note))
+  end
+
+  expose :path do |note|
+    if note.for_personal_snippet?
+      snippet_note_path(note.noteable, note)
+    else
+      namespace_project_note_path(note.project.namespace, note.project, note)
+    end
+  end
+
+  expose :attachment, using: NoteAttachmentEntity
+  expose :delete_attachment_path, if: -> (note, _) { note.attachment? } do |note|
+    delete_attachment_namespace_project_note_path(note.project.namespace, note.project, note)
+  end
+end
diff --git a/app/serializers/note_serializer.rb b/app/serializers/note_serializer.rb
new file mode 100644
index 00000000000..2afe40d7a34
--- /dev/null
+++ b/app/serializers/note_serializer.rb
@@ -0,0 +1,3 @@
+class NoteSerializer < BaseSerializer
+  entity NoteEntity
+end
diff --git a/app/serializers/user_entity.rb b/app/serializers/user_entity.rb
index 876512b12dc..3bb340065c4 100644
--- a/app/serializers/user_entity.rb
+++ b/app/serializers/user_entity.rb
@@ -1,6 +1,8 @@
 class UserEntity < API::Entities::UserBasic
   include RequestAwareEntity
 
+  unexpose :web_url
+
   expose :path do |user|
     user_path(user)
   end
diff --git a/app/views/discussions/_headline.html.haml b/app/views/discussions/_headline.html.haml
index c1dabeed387..25e90924413 100644
--- a/app/views/discussions/_headline.html.haml
+++ b/app/views/discussions/_headline.html.haml
@@ -5,7 +5,7 @@
       by
       = link_to_member(@project, discussion.resolved_by, avatar: false)
     = time_ago_with_tooltip(discussion.resolved_at, placement: "bottom")
-- elsif discussion.last_updated_at != discussion.created_at
+- elsif discussion.updated?
   .discussion-headline-light.js-discussion-headline
     Last updated
     - if discussion.last_updated_by
diff --git a/config/routes/project.rb b/config/routes/project.rb
index 672b5a9a160..d6fb309de8e 100644
--- a/config/routes/project.rb
+++ b/config/routes/project.rb
@@ -308,6 +308,7 @@ constraints(ProjectUrlConstrainer.new) do
           get :can_create_branch
           get :realtime_changes
           post :create_merge_request
+          get :discussions, format: :json
         end
         collection do
           post  :bulk_update
diff --git a/lib/api/entities.rb b/lib/api/entities.rb
index 09a88869063..89ab2118dd5 100644
--- a/lib/api/entities.rb
+++ b/lib/api/entities.rb
@@ -1,11 +1,11 @@
 module API
   module Entities
     class UserSafe < Grape::Entity
-      expose :name, :username
+      expose :id, :name, :username
     end
 
     class UserBasic < UserSafe
-      expose :id, :state
+      expose :state
       expose :avatar_url do |user, options|
         user.avatar_url(only_path: false)
       end