Watch num_tablet_servers_live against your node count; a drop means a tablet server failed heartbeats or is partitioned, often from clock skew. If hybrid_clock_skew is approaching hybrid_clock_error, fix clock sync on that host before reads start restarting. YSQL counters only move under load, so exercise the cluster before concluding metrics are broken.

Context: Instrumentation runbook: documents the gotcha that an idle YugabyteDB cluster shows no datapoints for YSQL counters, and that a dropped tablet server is the first suspect when num_tablet_servers_live falls below the node count. When hybrid_clock_skew approaches hybrid_clock_error, the node is at risk of read restarts and stalls, so check NTP or chrony on that host.

## Matched source
Source: Published skill
Original query: "YugabyteDB tablet server drops and skew show up in server metrics first"
Key terms: drops, first, metrics, server, show, skew, tablet, yugabytedb