diff --git a/modules/tests-ui/models.js b/modules/tests-ui/models.js
index 5f5ab8f18..9e3291ea2 100644
--- a/modules/tests-ui/models.js
+++ b/modules/tests-ui/models.js
@@ -92,6 +92,9 @@
         return this.errors_list && this.errors_list.length > 0;
     };
 
+    // Used in `loadPluginTests`, `loadTestSets`, `removeOldSets`.
+    TestUrlsSetSchema.index({plugin: 1, created_at: -1});
+
     var PageTestLogSchema = new Schema({
 
         url: {
@@ -151,6 +154,9 @@
         return moment(this.created_at).format("DD-MM-YY HH:mm");
     };
 
+    // Used in `checkPageTestLogChangeNotification`.
+    PageTestLogSchema.index({plugin: 1, url: 1, created_at: -1});
+
     export const PluginTest = db.model('PluginTest', PluginTestSchema);
     export const PageTestLog = db.model('PageTestLog', PageTestLogSchema);
     export const TestUrlsSet = db.model('TestUrlsSet', TestUrlsSetSchema);
diff --git a/modules/tests-ui/tester.js b/modules/tests-ui/tester.js
index 537024663..d1f719872 100644
--- a/modules/tests-ui/tester.js
+++ b/modules/tests-ui/tester.js
@@ -50,6 +50,8 @@ var PageTestLog = models.PageTestLog;
 var TestUrlsSet = models.TestUrlsSet;
 var TestingProgress = models.TestingProgress;
 
+var OLD_LOGS_MONTH_TTL = 30 * 24 * 60 * 60 * 1000;
+
 function log() {
     if (CONFIG.DEBUG) {
         console.log.apply(console, arguments);
@@ -134,8 +136,8 @@ function checkPageTestLogChangeNotification(logEntry) {
 
     PageTestLog
         .find({
-            url: logEntry.url,
             plugin: logEntry.plugin,    
+            url: logEntry.url,
             created_at: {
                 $lt: logEntry.created_at
             }
@@ -146,6 +148,19 @@ function checkPageTestLogChangeNotification(logEntry) {
 
             previousLogEntry = previousLogEntry && previousLogEntry.length && previousLogEntry[0];
 
+            if (previousLogEntry) {
+                // Keep only current and previous log per plugin+url, older ones are unused.
+                PageTestLog.deleteMany({
+                    plugin: logEntry.plugin,
+                    url: logEntry.url,
+                    created_at: {
+                        $lt: previousLogEntry.created_at
+                    }
+                }).catch(function(error) {
+                    cerror('Error removing old page test logs', error);
+                });
+            }
+
             /*
 
             Case 1.
@@ -564,6 +579,24 @@ function processPluginTests(pluginTest, plugin, count, cb) {
                     cb(null, data);
                 })
                 .catch(cb);
+        },
+
+        function removeOldLogs(data, cb) {
+            // Logs of urls no longer in the current set.
+            PageTestLog.deleteMany({
+                plugin: plugin.id,
+                url: {
+                    $nin: testUrlsSet.urls
+                },
+                created_at: {
+                    // Remove only old.
+                    $lt: new Date(new Date() - OLD_LOGS_MONTH_TTL)
+                }
+            })
+                .then(data => {
+                    cb(null, data);
+                })
+                .catch(cb);
         }
 
     ], cb);
@@ -604,7 +637,26 @@ function testAll(cb) {
             ], cb);
         },
 
-        function loadPluginTests(data, cb) {
+        function cleanupObsoleteData(data, cb) {
+            PluginTest.find({obsolete: true}).distinct('_id')
+                .then(obsoleteIds => {
+                    if (obsoleteIds.length === 0) {
+                        return Promise.resolve();
+                    }
+                    // Keep recent data in case plugin comes back soon.
+                    var monthAgo = new Date(new Date() - OLD_LOGS_MONTH_TTL);
+                    return Promise.all([
+                        TestUrlsSet.deleteMany({plugin: {$in: obsoleteIds}, created_at: {$lt: monthAgo}}),
+                        PageTestLog.deleteMany({plugin: {$in: obsoleteIds}, created_at: {$lt: monthAgo}})
+                    ]);
+                })
+                .then(() => {
+                    cb();
+                })
+                .catch(cb);
+        },
+
+        function loadPluginTests(cb) {
 
             if (testOnePlugin) {
                 PluginTest.find({_id: testOnePlugin})