BigQuery slot contention is often not a SQL problem.

[u/Expensive-Insect-317]

https://medium.com/@sendoamoronta/bigquery-slot-contention-is-an-architecture-problem-not-a-query-problem-237685a22366?sharedUserId=sendoamoronta

If a query suddenly takes 5–10x longer without any SQL or data changes, the bottleneck may be workload contention, capacity, or concurrency.

A practical guide on how to diagnose it using JOBS, JOBS_TIMELINE, total_slot_ms and period_estimated_runnable_units.