Microsoft Defender for Azure SQL Slowdown

Iain Evans finds a hidden cost:

To find the root cause, we conducted a configuration comparison of the servers against an Aireforge configuration snapshot to check for any changes. We immediately noticed that an extended event session called SQLAdvancedThreatProtectionTraffic had recently been deployed. This session is deployed by default with Azure Defender for SQL Server. More info: https://learn.microsoft.com/en-us/azure/defender-for-cloud/defender-for-sql-introduction#advanced-threat-protection

Read on to see what the symptoms were and what kind of impact this had.