> Is there a change-detection service like this, being provided with stable SLAs by one of the cloud IaaS providers?
You're looking for Zyte (formerly ScrapingHub).
You're looking for Zyte (formerly ScrapingHub).
Are you sure? it seems focused on scraping/crawling/data extraction, and I'm not seeing any built-in capabilities to (for example) simply trigger a callback when a resource changes.