When a SEO URL gets deleted, for example when deleting a category, the row in the seourl table is not really removed. Instead the 'isdeleted' flag gets set to true. For big tables like the seourl, this is actually quite good behaviour, as it is much faster than deleting a row and rebuilding all indices.
However, after some time, the database table can grow very large with inactive "isdeleted = true" rows.
Proposal: add a cleanup task that actually deletes the rows that have "is_deleted = true"