How to Optimize BigQuery Costs (Real Techniques That Work)

I want to start with a number: $140,000 . That's how much a single misconfigured scheduled query cost one of the teams I worked with over a three-month period. Not a rogue machine learning job. Not a massive ETL pipeline. A scheduled query. Running every 15 minutes. Scanning a 4TB table every time. For 90 days before anyone looked at the bill closely enough to notice. Nobody wrote that query with malicious intent. The engineer who wrote it was experienced. The table had been small when the query