Referring the Developer Docs of SFMC, Source: Here , it mentions that performance shows degradation if rows in data extension exceed 100 million rows.
I need to know whether Data Retention can be applied retroactively on a Data Extension with over 100 million rows.
Yes, you can enable data retention for Data Extensions with existing records.
However all existing records will have the start time set to when you set the retention. This is because the entry time of a record to a DE (hidden field _CreatedDate) does not exist until you set a data retention rule.
So if you set retention period to 30 days, you will remove all of the existing records 30 days from now, and new records will each be removed 30 days after their creation date.
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