diff --git a/common/models/user.json b/common/models/user.json
index 01a3b3a6bc15f0..bc5e5796049d1b 100644
--- a/common/models/user.json
+++ b/common/models/user.json
@@ -88,39 +88,6 @@
     "google": {
       "type": "string"
     },
-    "completedBonfires": {
-      "type": [
-        {
-          "id": "string",
-          "name": "string",
-          "completedWith": "string",
-          "completedDate": "string",
-          "solution": "string"
-        }
-      ],
-      "default": []
-    },
-    "uncompletedCoursewares": {
-      "type": "array",
-      "default": []
-    },
-    "completedCoursewares": {
-      "type": [
-        {
-          "completedDate": {
-            "type": "string",
-            "defaultFn": "now"
-          },
-          "id": "string",
-          "name": "string",
-          "completedWith": "string",
-          "solution": "string",
-          "githubLink": "string",
-          "verified": "boolean"
-        }
-      ],
-      "default": []
-    },
     "currentStreak": {
       "type": "number",
       "default": 0
@@ -140,10 +107,15 @@
     "currentChallenge": {
       "type": {}
     },
+    "isUniqMigrated": {
+      "type": "boolean",
+      "default": false
+    },
     "completedChallenges": {
       "type": [
         {
           "completedDate": "number",
+          "lastUpdated": "number",
           "id": "string",
           "name": "string",
           "completedWith": "string",
diff --git a/server/boot/challenge.js b/server/boot/challenge.js
index 1102da7f626d77..b8b5ed60f4f74e 100644
--- a/server/boot/challenge.js
+++ b/server/boot/challenge.js
@@ -34,22 +34,52 @@ const dasherize = utils.dasherize;
 const unDasherize = utils.unDasherize;
 const getMDNLinks = utils.getMDNLinks;
 
+function makeChallengesUnique(challengeArr) {
+  // clone and reverse challenges
+  // then filter by unique id's
+  // then reverse again
+  return _.uniq(challengeArr.slice().reverse(), 'id').reverse();
+}
 function numberWithCommas(x) {
   return x.toString().replace(/\B(?=(\d{3})+(?!\d))/g, ',');
 }
 
 function updateUserProgress(user, challengeId, completedChallenge) {
-  const alreadyCompleted = user.completedChallenges.some(({ id }) => {
-    return id === challengeId;
+  let { completedChallenges } = user;
+
+  // migrate user challenges object to remove
+  if (!user.isUniqMigrated) {
+    user.isUniqMigrated = true;
+
+    completedChallenges = user.completedChallenges =
+      makeChallengesUnique(completedChallenges);
+  }
+
+  const indexOfChallenge = _.findIndex(completedChallenges, {
+    id: challengeId
   });
 
+  const alreadyCompleted = indexOfChallenge !== -1;
+
   if (!alreadyCompleted) {
     user.progressTimestamps.push({
       timestamp: Date.now(),
-      completedChallenge
+      completedChallenge: challengeId
     });
+    user.completedChallenges.push(completedChallenge);
+    return user;
   }
-  user.completedChallenges.push(completedChallenge);
+
+  const oldCompletedChallenge = completedChallenges[indexOfChallenge];
+  user.completedChallenges[indexOfChallenge] =
+    Object.assign(
+      {},
+      completedChallenge,
+      {
+        completedDate: oldCompletedChallenge.completedDate,
+        lastUpdated: completedChallenge.completedDate
+      }
+    );
   return user;
 }