# Cluster Query Latency

## Question

Which shared execution or wait boundary explains the overall or multi-query
latency increase at the affected service, instance and incident window?

## Enter When

Use for overall runtime, P99/P999, multi-query latency or symptom-led slow-query
discovery without a selected SQL target. A SQL mentioned as a suspected
explanation remains comparison context. Diagnosis and tuning of a particular
SQL belongs to single-query; do not perform that audit here by default.
The Router also selects workload-hotspot as an independent workload-concentration
alternative for an overall latency incident.

## First Evidence Question

Align the overall latency distribution and affected scope to the incident.
Compare representative Slow Query phase and wait facts with that signal:
total elapsed time, execution, storage/coprocessor, locks, backoff, resource
queues and result-response time, only where the Provider supports them.

Broad lists omit SQL text and detailed plans. Retain full Digests, instance,
execution timestamps, durations and selected numeric fields. This is deliberate
evidence selection, not failed acquisition or unavailable SQL capability.
Do not request every SQL text or fetch plans for every representative record.

TopSQL is not a completion gate here: workload-hotspot owns concentration.
Use it only for a precise secondary question not answered by the current facts.

## Decision

Distinguish a widespread delay from a few isolated slow executions. Slow Query
top-N is not the workload distribution and cannot by itself explain P99.
Align the same entity/window and preserve sample and source limitations.
Do not call a wall-clock delay CPU-heavy without aligned CPU/execution evidence.

## Strongest Alternative and Stop

Diagnose from the distribution and phase facts first. Refine by one selected
Digest only when its SQL or plan content can distinguish a newly discovered
load-bearing mechanism. Missing SQL text in a broad list is not a refinement
reason. Stop at a supported shared mechanism or the exact remaining limitation.