diff --git a/src/infrastructure/daemon/workers/query/PhabricatorWorkerLeaseQuery.php b/src/infrastructure/daemon/workers/query/PhabricatorWorkerLeaseQuery.php
index 8cbf4eaf8b..d4996e3e35 100644
--- a/src/infrastructure/daemon/workers/query/PhabricatorWorkerLeaseQuery.php
+++ b/src/infrastructure/daemon/workers/query/PhabricatorWorkerLeaseQuery.php
@@ -48,21 +48,43 @@ final class PhabricatorWorkerLeaseQuery extends PhabricatorQuery {
 
     $leased = 0;
     foreach ($phases as $phase) {
-      queryfx(
+
+      // NOTE: If we issue `UPDATE ... WHERE ... ORDER BY id ASC`, the query
+      // goes very, very slowly. The `ORDER BY` triggers this, although we get
+      // the same apparent results without it. Without the ORDER BY, binary
+      // read slaves complain that the query isn't repeatable. To avoid both
+      // problems, do a SELECT and then an UPDATE.
+
+      $rows = queryfx_all(
         $conn_w,
-        'UPDATE %T task
-          SET leaseOwner = %s, leaseExpires = UNIX_TIMESTAMP() + %d
-          %Q %Q %Q',
+        'SELECT id, leaseOwner FROM %T %Q %Q %Q',
         $task_table->getTableName(),
-        $lease_ownership_name,
-        self::DEFAULT_LEASE_DURATION,
         $this->buildWhereClause($conn_w, $phase),
         $this->buildOrderClause($conn_w),
         $this->buildLimitClause($conn_w, $limit - $leased));
 
-      $leased += $conn_w->getAffectedRows();
-      if ($leased == $limit) {
-        break;
+      // NOTE: Sometimes, we'll race with another worker and they'll grab
+      // this task before we do. We could reduce how often this happens by
+      // selecting more tasks than we need, then shuffling them and trying
+      // to lock only the number we're actually after. However, the amount
+      // of time workers spend here should be very small relative to their
+      // total runtime, so keep it simple for the moment.
+
+      if ($rows) {
+        queryfx(
+          $conn_w,
+          'UPDATE %T task
+            SET leaseOwner = %s, leaseExpires = UNIX_TIMESTAMP() + %d
+            %Q',
+          $task_table->getTableName(),
+          $lease_ownership_name,
+          self::DEFAULT_LEASE_DURATION,
+          $this->buildUpdateWhereClause($conn_w, $phase, $rows));
+
+        $leased += $conn_w->getAffectedRows();
+        if ($leased == $limit) {
+          break;
+        }
       }
     }
 
@@ -124,6 +146,48 @@ final class PhabricatorWorkerLeaseQuery extends PhabricatorQuery {
     return $this->formatWhereClause($where);
   }
 
+  private function buildUpdateWhereClause(
+    AphrontDatabaseConnection $conn_w,
+    $phase,
+    array $rows) {
+
+    $where = array();
+
+    // NOTE: This is basically working around the MySQL behavior that
+    // `IN (NULL)` doesn't match NULL.
+
+    switch ($phase) {
+      case self::PHASE_UNLEASED:
+        $where[] = qsprintf(
+          $conn_w,
+          'leaseOwner IS NULL');
+        $where[] = qsprintf(
+          $conn_w,
+          'id IN (%Ld)',
+          ipull($rows, 'id'));
+        break;
+      case self::PHASE_EXPIRED:
+        $in = array();
+        foreach ($rows as $row) {
+          $in[] = qsprintf(
+            $conn_w,
+            '(%d, %s)',
+            $row['id'],
+            $row['leaseOwner']);
+        }
+        $where[] = qsprintf(
+          $conn_w,
+          '(id, leaseOwner) IN (%Q)',
+          '('.implode(', ', $in).')');
+        break;
+      default:
+        throw new Exception("Unknown phase '{$phase}'!");
+    }
+
+    return $this->formatWhereClause($where);
+
+  }
+
   private function buildOrderClause(AphrontDatabaseConnection $conn_w) {
     return qsprintf($conn_w, 'ORDER BY id ASC');
   }