Each tool's output decides which tool comes next.
Not three independent, parallel checks.
Cloud TraceWhich service is slow?
Cloud ProfilerWhich function in that service?
Query InsightsWhich query, with what plan?
Index advisorWhat index is missing?
Query Insights had correctly flagged an index-missing query for weeks, visible the whole time — nobody had a standing habit of checking it, since the regression never crossed a single-day alert threshold. The gap was process, not tooling.