Answer
Sudden regressions often occur due to:
- Updated statistics
- Parameter sniffing plan changes
- Index changes
- Fragmentation spikes
- Failover causing cold cache
- Data growth affecting plan shapes
Quick Answer
Plan regressions after stats updates (optimizer uses new distribution data), index rebuilds (resets statistics), database compatibility level changes (new CE model), and SQL Server upgrades. Queries that were fast can suddenly get a different plan that's wrong for current data. Query Store is the primary tool to detect and revert regressions.
S
SugharaIQ Editorial Team
Verified Answer
This answer has been peer-reviewed by industry experts holding senior engineering roles to ensure technical accuracy and relevance for modern interview standards.
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Source: SugharaIQ