upgrade notes: explain performance benefits

Author: valentijnscholten

docs/content/en/open_source/upgrading/2.51.md

@@ -5,6 +5,16 @@ weight: -20250902
 description: Helm chart changes and Postgres major version updates.
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+## Performance improvements
+
+This release includes multiple improvements aimed at making DefectDojo faster, more scalable, and lighter on your database and workers.
+
+- Import and reimport are significantly more efficient: product grading is now orchestrated in batches using Celery chords, reducing the number of background tasks and database churn during large scans. This means faster imports and smoother post-processing on busy systems. See [PR 12914](https://github.com/DefectDojo/django-DefectDojo/pull/12914).
+- Query-count reductions and importer hot-path tuning: we trimmed unnecessary ORM calls and optimized how findings/endpoints are updated during (re)import. You should see noticeably quicker runs out of the box. See [PR 13182](https://github.com/DefectDojo/django-DefectDojo/pull/13182) and [PR 13152](https://github.com/DefectDojo/django-DefectDojo/pull/13152).
+- Smarter background task orchestration and general cleanup: less duplicate work and better scheduling during heavy operations, keeping the UI responsive while long jobs run. See [PR 12900](https://github.com/DefectDojo/django-DefectDojo/pull/12900).
+
+No configuration changes are required—gains are automatic after upgrading.
+
 ## Helm Chart Changes
 
 This release introduces several important changes to the Helm chart configuration: