but you don't need to compare on each page request - only if you update your data. Sorry, if I didn't state that clearly :-)
But I assume here your observation is wrong!
Continuing the tool documentation that would mean, that you might update the data may be once a week or once a month. So all queries to the DB would waste capacity, or not? If no data changed, we don't need to change the document and so we don't need to process the output for each requesting client.
The only concern I have is the use of SSI. That is the point where I am afraid to loose time and if it wouldn't be better to compose the documents upon content creation.

Have a nice day
All decision is left to your taste