diff --git a/app/assets/javascripts/diffs/components/diff_line_gutter_content.vue b/app/assets/javascripts/diffs/components/diff_line_gutter_content.vue
index 0fe0007057b..d184a76f038 100644
--- a/app/assets/javascripts/diffs/components/diff_line_gutter_content.vue
+++ b/app/assets/javascripts/diffs/components/diff_line_gutter_content.vue
@@ -71,6 +71,11 @@ export default {
       required: false,
       default: false,
     },
+    discussions: {
+      type: Array,
+      required: false,
+      default: () => [],
+    },
   },
   computed: {
     ...mapState({
@@ -78,7 +83,6 @@ export default {
       diffFiles: state => state.diffs.diffFiles,
     }),
     ...mapGetters(['isLoggedIn']),
-    ...mapGetters('diffs', ['discussionsByLineCode']),
     lineHref() {
       return this.lineCode ? `#${this.lineCode}` : '#';
     },
@@ -88,24 +92,19 @@ export default {
         this.showCommentButton &&
         !this.isMatchLine &&
         !this.isContextLine &&
-        !this.hasDiscussions &&
-        !this.isMetaLine
+        !this.isMetaLine &&
+        !this.hasDiscussions
       );
     },
-    discussions() {
-      return this.discussionsByLineCode[this.lineCode] || [];
-    },
     hasDiscussions() {
       return this.discussions.length > 0;
     },
     shouldShowAvatarsOnGutter() {
-      let render = this.hasDiscussions && this.showCommentButton;
-
       if (!this.lineType && this.linePosition === LINE_POSITION_RIGHT) {
-        render = false;
+        return false;
       }
 
-      return render;
+      return this.hasDiscussions && this.showCommentButton;
     },
   },
   methods: {
diff --git a/app/assets/javascripts/diffs/components/diff_table_cell.vue b/app/assets/javascripts/diffs/components/diff_table_cell.vue
index 5962f30d9bb..e8e8ddc6c5e 100644
--- a/app/assets/javascripts/diffs/components/diff_table_cell.vue
+++ b/app/assets/javascripts/diffs/components/diff_table_cell.vue
@@ -67,6 +67,11 @@ export default {
       required: false,
       default: false,
     },
+    discussions: {
+      type: Array,
+      required: false,
+      default: () => [],
+    },
   },
   computed: {
     ...mapGetters(['isLoggedIn']),
@@ -136,6 +141,7 @@ export default {
       :is-match-line="isMatchLine"
       :is-context-line="isContentLine"
       :is-meta-line="isMetaLine"
+      :discussions="discussions"
     />
   </td>
 </template>
diff --git a/app/assets/javascripts/diffs/components/inline_diff_comment_row.vue b/app/assets/javascripts/diffs/components/inline_diff_comment_row.vue
index a6f011ff31e..1b5ae5e9f75 100644
--- a/app/assets/javascripts/diffs/components/inline_diff_comment_row.vue
+++ b/app/assets/javascripts/diffs/components/inline_diff_comment_row.vue
@@ -1,5 +1,5 @@
 <script>
-import { mapState, mapGetters } from 'vuex';
+import { mapState } from 'vuex';
 import diffDiscussions from './diff_discussions.vue';
 import diffLineNoteForm from './diff_line_note_form.vue';
 
@@ -21,15 +21,16 @@ export default {
       type: Number,
       required: true,
     },
+    discussions: {
+      type: Array,
+      required: false,
+      default: () => [],
+    },
   },
   computed: {
     ...mapState({
       diffLineCommentForms: state => state.diffs.diffLineCommentForms,
     }),
-    ...mapGetters('diffs', ['discussionsByLineCode']),
-    discussions() {
-      return this.discussionsByLineCode[this.line.lineCode] || [];
-    },
     className() {
       return this.discussions.length ? '' : 'js-temp-notes-holder';
     },
diff --git a/app/assets/javascripts/diffs/components/inline_diff_table_row.vue b/app/assets/javascripts/diffs/components/inline_diff_table_row.vue
index 0e306f39a9f..32d65ff994f 100644
--- a/app/assets/javascripts/diffs/components/inline_diff_table_row.vue
+++ b/app/assets/javascripts/diffs/components/inline_diff_table_row.vue
@@ -33,6 +33,11 @@ export default {
       required: false,
       default: false,
     },
+    discussions: {
+      type: Array,
+      required: false,
+      default: () => [],
+    },
   },
   data() {
     return {
@@ -89,6 +94,7 @@ export default {
       :is-bottom="isBottom"
       :is-hover="isHover"
       :show-comment-button="true"
+      :discussions="discussions"
       class="diff-line-num old_line"
     />
     <diff-table-cell
@@ -98,6 +104,7 @@ export default {
       :line-type="newLineType"
       :is-bottom="isBottom"
       :is-hover="isHover"
+      :discussions="discussions"
       class="diff-line-num new_line"
     />
     <td
diff --git a/app/assets/javascripts/diffs/components/inline_diff_view.vue b/app/assets/javascripts/diffs/components/inline_diff_view.vue
index 8e491d293e5..5f30cc57a59 100644
--- a/app/assets/javascripts/diffs/components/inline_diff_view.vue
+++ b/app/assets/javascripts/diffs/components/inline_diff_view.vue
@@ -20,7 +20,11 @@ export default {
     },
   },
   computed: {
-    ...mapGetters('diffs', ['commitId', 'discussionsByLineCode']),
+    ...mapGetters('diffs', [
+      'commitId',
+      'shouldRenderInlineCommentRow',
+      'singleDiscussionByLineCode',
+    ]),
     ...mapState({
       diffLineCommentForms: state => state.diffs.diffLineCommentForms,
     }),
@@ -34,18 +38,7 @@ export default {
       return window.gon.user_color_scheme;
     },
   },
-  methods: {
-    shouldRenderCommentRow(line) {
-      if (this.diffLineCommentForms[line.lineCode]) return true;
-
-      const lineDiscussions = this.discussionsByLineCode[line.lineCode];
-      if (lineDiscussions === undefined) {
-        return false;
-      }
-
-      return lineDiscussions.every(discussion => discussion.expanded);
-    },
-  },
+  methods: {},
 };
 </script>
 
@@ -64,13 +57,15 @@ export default {
           :line="line"
           :is-bottom="index + 1 === diffLinesLength"
           :key="line.lineCode"
+          :discussions="singleDiscussionByLineCode(line.lineCode)"
         />
         <inline-diff-comment-row
-          v-if="shouldRenderCommentRow(line)"
+          v-if="shouldRenderInlineCommentRow(line)"
           :diff-file-hash="diffFile.fileHash"
           :line="line"
           :line-index="index"
           :key="index"
+          :discussions="singleDiscussionByLineCode(line.lineCode)"
         />
       </template>
     </tbody>
diff --git a/app/assets/javascripts/diffs/components/parallel_diff_comment_row.vue b/app/assets/javascripts/diffs/components/parallel_diff_comment_row.vue
index 05e5cafc717..bb9a65c83fa 100644
--- a/app/assets/javascripts/diffs/components/parallel_diff_comment_row.vue
+++ b/app/assets/javascripts/diffs/components/parallel_diff_comment_row.vue
@@ -1,5 +1,5 @@
 <script>
-import { mapState, mapGetters } from 'vuex';
+import { mapState } from 'vuex';
 import diffDiscussions from './diff_discussions.vue';
 import diffLineNoteForm from './diff_line_note_form.vue';
 
@@ -21,48 +21,51 @@ export default {
       type: Number,
       required: true,
     },
+    leftDiscussions: {
+      type: Array,
+      required: false,
+      default: () => [],
+    },
+    rightDiscussions: {
+      type: Array,
+      required: false,
+      default: () => [],
+    },
   },
   computed: {
     ...mapState({
       diffLineCommentForms: state => state.diffs.diffLineCommentForms,
     }),
-    ...mapGetters('diffs', ['discussionsByLineCode']),
     leftLineCode() {
       return this.line.left.lineCode;
     },
     rightLineCode() {
       return this.line.right.lineCode;
     },
-    hasDiscussion() {
-      const discussions = this.discussionsByLineCode;
-
-      return discussions[this.leftLineCode] || discussions[this.rightLineCode];
-    },
     hasExpandedDiscussionOnLeft() {
-      const discussions = this.discussionsByLineCode[this.leftLineCode];
-
+      const discussions = this.leftDiscussions;
       return discussions ? discussions.every(discussion => discussion.expanded) : false;
     },
     hasExpandedDiscussionOnRight() {
-      const discussions = this.discussionsByLineCode[this.rightLineCode];
-
+      const discussions = this.rightDiscussions;
       return discussions ? discussions.every(discussion => discussion.expanded) : false;
     },
     hasAnyExpandedDiscussion() {
       return this.hasExpandedDiscussionOnLeft || this.hasExpandedDiscussionOnRight;
     },
     shouldRenderDiscussionsOnLeft() {
-      return this.discussionsByLineCode[this.leftLineCode] && this.hasExpandedDiscussionOnLeft;
+      return this.leftDiscussions && this.hasExpandedDiscussionOnLeft;
     },
     shouldRenderDiscussionsOnRight() {
-      return (
-        this.discussionsByLineCode[this.rightLineCode] &&
-        this.hasExpandedDiscussionOnRight &&
-        this.line.right.type
-      );
+      return this.rightDiscussions && this.hasExpandedDiscussionOnRight && this.line.right.type;
+    },
+    showRightSideCommentForm() {
+      return this.line.right.type && this.diffLineCommentForms[this.rightLineCode];
     },
     className() {
-      return this.hasDiscussion ? '' : 'js-temp-notes-holder';
+      return this.leftDiscussions.length > 0 || this.rightDiscussions.length > 0
+        ? ''
+        : 'js-temp-notes-holder';
     },
   },
 };
@@ -80,13 +83,12 @@ export default {
         class="content"
       >
         <diff-discussions
-          v-if="discussionsByLineCode[leftLineCode].length"
-          :discussions="discussionsByLineCode[leftLineCode]"
+          v-if="leftDiscussions.length"
+          :discussions="leftDiscussions"
         />
       </div>
       <diff-line-note-form
-        v-if="diffLineCommentForms[leftLineCode] &&
-        diffLineCommentForms[leftLineCode]"
+        v-if="diffLineCommentForms[leftLineCode]"
         :diff-file-hash="diffFileHash"
         :line="line.left"
         :note-target-line="line.left"
@@ -100,13 +102,12 @@ export default {
         class="content"
       >
         <diff-discussions
-          v-if="discussionsByLineCode[rightLineCode].length"
-          :discussions="discussionsByLineCode[rightLineCode]"
+          v-if="rightDiscussions.length"
+          :discussions="rightDiscussions"
         />
       </div>
       <diff-line-note-form
-        v-if="diffLineCommentForms[rightLineCode] &&
-        diffLineCommentForms[rightLineCode] && line.right.type"
+        v-if="showRightSideCommentForm"
         :diff-file-hash="diffFileHash"
         :line="line.right"
         :note-target-line="line.right"
diff --git a/app/assets/javascripts/diffs/components/parallel_diff_table_row.vue b/app/assets/javascripts/diffs/components/parallel_diff_table_row.vue
index 0031cedc68f..d4e54c2bd00 100644
--- a/app/assets/javascripts/diffs/components/parallel_diff_table_row.vue
+++ b/app/assets/javascripts/diffs/components/parallel_diff_table_row.vue
@@ -36,6 +36,16 @@ export default {
       required: false,
       default: false,
     },
+    leftDiscussions: {
+      type: Array,
+      required: false,
+      default: () => [],
+    },
+    rightDiscussions: {
+      type: Array,
+      required: false,
+      default: () => [],
+    },
   },
   data() {
     return {
@@ -116,6 +126,7 @@ export default {
       :is-hover="isLeftHover"
       :show-comment-button="true"
       :diff-view-type="parallelDiffViewType"
+      :discussions="leftDiscussions"
       class="diff-line-num old_line"
     />
     <td
@@ -136,6 +147,7 @@ export default {
       :is-hover="isRightHover"
       :show-comment-button="true"
       :diff-view-type="parallelDiffViewType"
+      :discussions="rightDiscussions"
       class="diff-line-num new_line"
     />
     <td
diff --git a/app/assets/javascripts/diffs/components/parallel_diff_view.vue b/app/assets/javascripts/diffs/components/parallel_diff_view.vue
index 8f8d6bbc818..4d97cb6d15d 100644
--- a/app/assets/javascripts/diffs/components/parallel_diff_view.vue
+++ b/app/assets/javascripts/diffs/components/parallel_diff_view.vue
@@ -21,7 +21,11 @@ export default {
     },
   },
   computed: {
-    ...mapGetters('diffs', ['commitId', 'discussionsByLineCode']),
+    ...mapGetters('diffs', [
+      'commitId',
+      'singleDiscussionByLineCode',
+      'shouldRenderParallelCommentRow',
+    ]),
     ...mapState({
       diffLineCommentForms: state => state.diffs.diffLineCommentForms,
     }),
@@ -51,32 +55,6 @@ export default {
       return window.gon.user_color_scheme;
     },
   },
-  methods: {
-    shouldRenderCommentRow(line) {
-      const leftLineCode = line.left.lineCode;
-      const rightLineCode = line.right.lineCode;
-      const discussions = this.discussionsByLineCode;
-      const leftDiscussions = discussions[leftLineCode];
-      const rightDiscussions = discussions[rightLineCode];
-      const hasDiscussion = leftDiscussions || rightDiscussions;
-
-      const hasExpandedDiscussionOnLeft = leftDiscussions
-        ? leftDiscussions.every(discussion => discussion.expanded)
-        : false;
-      const hasExpandedDiscussionOnRight = rightDiscussions
-        ? rightDiscussions.every(discussion => discussion.expanded)
-        : false;
-
-      if (hasDiscussion && (hasExpandedDiscussionOnLeft || hasExpandedDiscussionOnRight)) {
-        return true;
-      }
-
-      const hasCommentFormOnLeft = this.diffLineCommentForms[leftLineCode];
-      const hasCommentFormOnRight = this.diffLineCommentForms[rightLineCode];
-
-      return hasCommentFormOnLeft || hasCommentFormOnRight;
-    },
-  },
 };
 </script>
 
@@ -97,13 +75,17 @@ export default {
             :line="line"
             :is-bottom="index + 1 === diffLinesLength"
             :key="index"
+            :left-discussions="singleDiscussionByLineCode(line.left.lineCode)"
+            :right-discussions="singleDiscussionByLineCode(line.right.lineCode)"
           />
           <parallel-diff-comment-row
-            v-if="shouldRenderCommentRow(line)"
+            v-if="shouldRenderParallelCommentRow(line)"
             :key="`dcr-${index}`"
             :line="line"
             :diff-file-hash="diffFile.fileHash"
             :line-index="index"
+            :left-discussions="singleDiscussionByLineCode(line.left.lineCode)"
+            :right-discussions="singleDiscussionByLineCode(line.right.lineCode)"
           />
         </template>
       </tbody>
diff --git a/app/assets/javascripts/diffs/store/getters.js b/app/assets/javascripts/diffs/store/getters.js
index d3881fa1a0a..c7b9b1a16e6 100644
--- a/app/assets/javascripts/diffs/store/getters.js
+++ b/app/assets/javascripts/diffs/store/getters.js
@@ -75,19 +75,21 @@ export const discussionsByLineCode = (state, getters, rootState, rootGetters) =>
     const isDiffDiscussion = note.diff_discussion;
     const hasLineCode = note.line_code;
     const isResolvable = note.resolvable;
-    const diffRefs = diffRefsByLineCode[note.line_code];
 
-    if (isDiffDiscussion && hasLineCode && isResolvable && diffRefs) {
-      const refs = convertObjectPropsToCamelCase(note.position.formatter);
-      const originalRefs = convertObjectPropsToCamelCase(note.original_position.formatter);
+    if (isDiffDiscussion && hasLineCode && isResolvable) {
+      const diffRefs = diffRefsByLineCode[note.line_code];
+      if (diffRefs) {
+        const refs = convertObjectPropsToCamelCase(note.position.formatter);
+        const originalRefs = convertObjectPropsToCamelCase(note.original_position.formatter);
 
-      if (_.isEqual(refs, diffRefs) || _.isEqual(originalRefs, diffRefs)) {
-        const lineCode = note.line_code;
+        if (_.isEqual(refs, diffRefs) || _.isEqual(originalRefs, diffRefs)) {
+          const lineCode = note.line_code;
 
-        if (acc[lineCode]) {
-          acc[lineCode].push(note);
-        } else {
-          acc[lineCode] = [note];
+          if (acc[lineCode]) {
+            acc[lineCode].push(note);
+          } else {
+            acc[lineCode] = [note];
+          }
         }
       }
     }
@@ -96,6 +98,47 @@ export const discussionsByLineCode = (state, getters, rootState, rootGetters) =>
   }, {});
 };
 
+export const singleDiscussionByLineCode = (state, getters) => lineCode => {
+  if (!lineCode) return [];
+  const discussions = getters.discussionsByLineCode;
+  return discussions[lineCode] || [];
+};
+
+export const shouldRenderParallelCommentRow = (state, getters) => line => {
+  const leftLineCode = line.left.lineCode;
+  const rightLineCode = line.right.lineCode;
+  const leftDiscussions = getters.singleDiscussionByLineCode(leftLineCode);
+  const rightDiscussions = getters.singleDiscussionByLineCode(rightLineCode);
+  const hasDiscussion = leftDiscussions.length || rightDiscussions.length;
+
+  const hasExpandedDiscussionOnLeft = leftDiscussions.length
+    ? leftDiscussions.every(discussion => discussion.expanded)
+    : false;
+  const hasExpandedDiscussionOnRight = rightDiscussions.length
+    ? rightDiscussions.every(discussion => discussion.expanded)
+    : false;
+
+  if (hasDiscussion && (hasExpandedDiscussionOnLeft || hasExpandedDiscussionOnRight)) {
+    return true;
+  }
+
+  const hasCommentFormOnLeft = state.diffLineCommentForms[leftLineCode];
+  const hasCommentFormOnRight = state.diffLineCommentForms[rightLineCode];
+
+  return hasCommentFormOnLeft || hasCommentFormOnRight;
+};
+
+export const shouldRenderInlineCommentRow = (state, getters) => line => {
+  if (state.diffLineCommentForms[line.lineCode]) return true;
+
+  const lineDiscussions = getters.singleDiscussionByLineCode(line.lineCode);
+  if (lineDiscussions.length === 0) {
+    return false;
+  }
+
+  return lineDiscussions.every(discussion => discussion.expanded);
+};
+
 // prevent babel-plugin-rewire from generating an invalid default during karma∂ tests
 export const getDiffFileByHash = state => fileHash =>
   state.diffFiles.find(file => file.fileHash === fileHash);
diff --git a/changelogs/unreleased/tz-mr-refactor-memory-reduction.yml b/changelogs/unreleased/tz-mr-refactor-memory-reduction.yml
new file mode 100644
index 00000000000..20b72c98bc1
--- /dev/null
+++ b/changelogs/unreleased/tz-mr-refactor-memory-reduction.yml
@@ -0,0 +1,5 @@
+---
+title: Reduces the client side memory footprint on merge requests
+merge_request: 20744
+author:
+type: performance
diff --git a/spec/javascripts/diffs/components/diff_line_gutter_content_spec.js b/spec/javascripts/diffs/components/diff_line_gutter_content_spec.js
index cb85d12daf2..bdc94131fc2 100644
--- a/spec/javascripts/diffs/components/diff_line_gutter_content_spec.js
+++ b/spec/javascripts/diffs/components/diff_line_gutter_content_spec.js
@@ -50,7 +50,11 @@ describe('DiffLineGutterContent', () => {
 
       it('should return discussions for the given lineCode', () => {
         const { lineCode } = getDiffFileMock().highlightedDiffLines[1];
-        const component = createComponent({ lineCode, showCommentButton: true });
+        const component = createComponent({
+          lineCode,
+          showCommentButton: true,
+          discussions: getDiscussionsMockData(),
+        });
 
         setDiscussions(component);