Even just the case of sitemap access alone can very well read half a database's tables and many of each table's columns in the act. That being done dozens of times a week between various search vendors and yeah your egress from just SEO can exceed the size of your database alone. Just depends on the nature of your data.
Then consider paging views, infinite scroll.
Then toss in something like Algolia or other third-party tools ingesting your data.
But it really boils down to your application. You might have NONE of these and egress is just crumbs.
Egress is defined as outbound traffic to the public internet.
Unless your database is publicly accessible (which it really should not be), its egress should be zero. What your /application/ returns to the public internet, is a different conversation.
Even just the case of sitemap access alone can very well read half a database's tables and many of each table's columns in the act. That being done dozens of times a week between various search vendors and yeah your egress from just SEO can exceed the size of your database alone. Just depends on the nature of your data.
Then consider paging views, infinite scroll.
Then toss in something like Algolia or other third-party tools ingesting your data.
But it really boils down to your application. You might have NONE of these and egress is just crumbs.