Limit the number of search results returned. This can be achieved by adjusting the ContentSearch.SearchMaxResults value to a lower number. Sitecore recommends to keep it at 500.

ContentSearch.SearchMaxResults.config

<?xml version="1.0" encoding="utf-8" ?>
<configuration xmlns:patch="http://www.sitecore.net/xmlconfig/" xmlns:set="http://www.sitecore.net/xmlconfig/set/" xmlns:role="http://www.sitecore.net/xmlconfig/role/" >
  <sitecore role:require="Standalone or ContentManagement">
    <settings>
      <setting name="ContentSearch.SearchMaxResults" set:value="500" />
    </settings>
  </sitecore>
</configuration>