How BigQuery actually executes a query (and why most optimization advice misses half the picture)

2026-05-11

BigQuery performance comes down to understanding its execution model: queries run as parallel stages across slots, and the main hidden cost is shuffle, not just bytes scanned. The Execution Details panel reveals stage-level slot-ms, max vs average compute time, and join strategy, making it possible to spot skew, fan-out, and expensive hash joins.