Database connections fail after maintenance

You connect to a managed database via the vendor's cluster DNS endpoint, which fronts a fleet of proxy nodes. The vendor ran a planned maintenance at 02:00 that cycled out half the proxy fleet. From 02:00–02:25 your app sees ~30% of new DB connections fail with 'connection refused' / timeouts, then it clears. Dashboards: failing connections target proxy IPs that were drained during maintenance; the vendor's cluster endpoint still resolved those IPs to your clients during the window. Your connection pool holds long-lived connections and your resolver caches the endpoint with a 60s TTL. How do you triage and mitigate?