GreptimeDB Performance Diagnosis

Help the user find the bottleneck behind a GreptimeDB performance problem, then point them at the right fix. This skill is the triage hub: it observes and concludes, it does not apply tuning itself. Once the cause is clear, hand off to:

• greptimedb-performance-tuning — server config and table-option changes (caches, write buffer, WAL, batching).
• greptimedb-table-design — schema changes (primary key, indexes, append-only, partitioning).

Before going deep, ask for the GreptimeDB version and deployment mode (standalone or cluster). Older versions may not expose some of the metrics below, and older Grafana dashboards may lack some panels — you can supplement them from the grafana dashboards directory, where each panel's PromQL is the canonical source for the metric names used below.