diff --git a/src/applications/feed/query/PhabricatorFeedQuery.php b/src/applications/feed/query/PhabricatorFeedQuery.php
--- a/src/applications/feed/query/PhabricatorFeedQuery.php
+++ b/src/applications/feed/query/PhabricatorFeedQuery.php
@@ -78,8 +78,8 @@
 
       $where[] = qsprintf(
         $conn,
-        'ref.chronologicalKey IN (%Q)',
-        implode(', ', $keys));
+        'ref.chronologicalKey IN (%LQ)',
+        $keys);
     }
 
     // NOTE: We may not have 64-bit PHP, so do the shifts in MySQL instead.
diff --git a/src/applications/harbormaster/step/HarbormasterBuildStepImplementation.php b/src/applications/harbormaster/step/HarbormasterBuildStepImplementation.php
--- a/src/applications/harbormaster/step/HarbormasterBuildStepImplementation.php
+++ b/src/applications/harbormaster/step/HarbormasterBuildStepImplementation.php
@@ -253,12 +253,32 @@
     HarbormasterBuildTarget $target,
     array $futures) {
 
+    $did_close = false;
+    $wait_start = PhabricatorTime::getNow();
+
     $futures = new FutureIterator($futures);
     foreach ($futures->setUpdateInterval(5) as $key => $future) {
-      if ($future === null) {
-        $build->reload();
-        if ($this->shouldAbort($build, $target)) {
-          throw new HarbormasterBuildAbortedException();
+      if ($future !== null) {
+        continue;
+      }
+
+      $build->reload();
+      if ($this->shouldAbort($build, $target)) {
+        throw new HarbormasterBuildAbortedException();
+      }
+
+      // See PHI916. If we're waiting on a remote system for a while, clean
+      // up database connections to reduce the cost of having a large number
+      // of processes babysitting an `ssh ... ./run-huge-build.sh` process on
+      // a build host.
+      if (!$did_close) {
+        $now = PhabricatorTime::getNow();
+        $elapsed = ($now - $wait_start);
+        $idle_limit = 5;
+
+        if ($elapsed >= $idle_limit) {
+          LiskDAO::closeIdleConnections();
+          $did_close = true;
         }
       }
     }
diff --git a/src/applications/search/index/PhabricatorIndexEngine.php b/src/applications/search/index/PhabricatorIndexEngine.php
--- a/src/applications/search/index/PhabricatorIndexEngine.php
+++ b/src/applications/search/index/PhabricatorIndexEngine.php
@@ -141,10 +141,10 @@
     queryfx(
       $conn_w,
       'INSERT INTO %T (objectPHID, extensionKey, version)
-        VALUES %Q
+        VALUES %LQ
         ON DUPLICATE KEY UPDATE version = VALUES(version)',
       $table->getTableName(),
-      implode(', ', $sql));
+      $sql);
   }
 
 }
diff --git a/src/applications/search/ngrams/PhabricatorSearchNgrams.php b/src/applications/search/ngrams/PhabricatorSearchNgrams.php
--- a/src/applications/search/ngrams/PhabricatorSearchNgrams.php
+++ b/src/applications/search/ngrams/PhabricatorSearchNgrams.php
@@ -102,9 +102,9 @@
     if ($sql) {
       queryfx(
         $conn_w,
-        'INSERT INTO %T (objectID, ngram) VALUES %Q',
+        'INSERT INTO %T (objectID, ngram) VALUES %LQ',
         $this->getTableName(),
-        implode(', ', $sql));
+        $sql);
     }
 
     return $this;
diff --git a/src/infrastructure/storage/lisk/LiskDAO.php b/src/infrastructure/storage/lisk/LiskDAO.php
--- a/src/infrastructure/storage/lisk/LiskDAO.php
+++ b/src/infrastructure/storage/lisk/LiskDAO.php
@@ -1652,6 +1652,11 @@
 
     $now = PhabricatorTime::getNow();
     foreach ($connections as $key => $connection) {
+      // If the connection is not idle, never consider it inactive.
+      if (!$connection->isIdle()) {
+        continue;
+      }
+
       $last_active = $connection->getLastActiveEpoch();
 
       $idle_duration = ($now - $last_active);
@@ -1672,6 +1677,18 @@
     }
   }
 
+  public static function closeIdleConnections() {
+    $connections = self::$connections;
+
+    foreach ($connections as $key => $connection) {
+      if (!$connection->isIdle()) {
+        continue;
+      }
+
+      self::closeConnection($key);
+    }
+  }
+
   private static function closeConnection($key) {
     if (empty(self::$connections[$key])) {
       throw new Exception(