diff --git a/source/upgrade/important-upgrade-notes.rst b/source/upgrade/important-upgrade-notes.rst
index 677f61ef13e..c68285d27e0 100644
--- a/source/upgrade/important-upgrade-notes.rst
+++ b/source/upgrade/important-upgrade-notes.rst
@@ -14,6 +14,36 @@ Important Upgrade Notes
 +----------------------------------------------------+------------------------------------------------------------------------------------------------------------------------------------------------------------------+
 | If you’re upgrading from a version earlier than... | Then...                                                                                                                                                          |
 +====================================================+==================================================================================================================================================================+
+| v9.1                                               | In v9.1.0, improved performance on data retention ``DeleteOrphanedRows`` queries.                                                                                |
+|                                                    |                                                                                                                                                                  |                                                                             
+|                                                    | New migration for a new table:                                                                                                                                   |
+|                                                    |                                                                                                                                                                  |
+|                                                    | MySQL:                                                                                                                                                           |
+|                                                    |                                                                                                                                                                  |
+|                                                    | ``CREATE TABLE IF NOT EXISTS RetentionIdsForDeletion (``                                                                                                         |
+|                                                    |     ``Id varchar(26) NOT NULL,``                                                                                                                                 |
+|                                                    |     ``TableName varchar(64),``                                                                                                                                   |
+|                                                    |     ``Ids json,``                                                                                                                                                |
+|                                                    |     ``PRIMARY KEY (Id),``                                                                                                                                        |
+|                                                    |     ``KEY idx_retentionidsfordeletion_tablename (TableName)``                                                                                                    |
+|                                                    | ``) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4;``                                                                                                                     |
+|                                                    |                                                                                                                                                                  |
+|                                                    | PostgreSQL:                                                                                                                                                      |
+|                                                    |                                                                                                                                                                  |
+|                                                    | ``CREATE TABLE IF NOT EXISTS retentionidsfordeletion (``                                                                                                         |
+|                                                    |     ``id varchar(26) PRIMARY KEY,``                                                                                                                              |       
+|                                                    |     ``tablename varchar(64),``                                                                                                                                   |
+|                                                    |     ``ids varchar(26)[]``                                                                                                                                        |
+|                                                    | ``);``                                                                                                                                                           |
+|                                                    | ``CREATE INDEX IF NOT EXISTS idx_retentionidsfordeletion_tablename ON retentionidsfordeletion (tablename);``                                                     |
+|                                                    |                                                                                                                                                                  | 
+|                                                    | Hard deleting a user or a channel will now also clean up associated reactions.                                                                                   |
+|                                                    |                                                                                                                                                                  | 
+|                                                    | Removed feature flag ``DataRetentionConcurrencyEnabled``. Data retention now runs without concurrency in order to avoid any performance degradation.             |
+|                                                    |                                                                                                                                                                  | 
+|                                                    | Added a new configuration setting ``DataRetentionSettings.RetentionIdsBatchSize``, which allows admins to configure how many batches of IDs will be fetched at   |
+|                                                    | a time when deleting orphaned reactions. The default value is 100.                                                                                               |
++----------------------------------------------------+------------------------------------------------------------------------------------------------------------------------------------------------------------------+
 | v9.0                                               | Removed the deprecated Insights feature.                                                                                                                         |
 |                                                    +------------------------------------------------------------------------------------------------------------------------------------------------------------------+
 |                                                    | Mattermost Boards and various other plugins have transitioned to being fully community supported. See this                                                       |