netes API server) to the Pilot instances in an eventually consistent manner. If the
<code>VirtualService</code> using the subsets arrives before the <code>DestinationRule</code> where the subsets are defined, the Envoy configuration generated by Pilot would refer to non-existent upstream pools. This results in HTTP 503 errors until all configuration objects are available to Pilot.</p><p>To make sure services will have zero down-time when configuring routes with subsets, follow a &ldquo;make-before-break&rdq