What is SQL Server automatic tuning and force last good plan mechanism?

Automatic tuning detects performance regressions and can revert to last known good execution plan.

SQL Server Automatic Tuning monitors query performance over time. If a new execution plan performs worse than a previous version, SQL Server can automatically revert to the last known good plan using plan forcing. This is based on runtime performance telemetry collected in Query Store. It helps stabilize workloads affected by plan regressions due to statistics changes or parameter sniffing.