I used to work at a company that provided APIs used for search/personalization/autosuggest for a whole bunch of huge e-commerce companies. Since the entire integration with the customer site was API based, we worked off of tracking pixels, API requests and cookies to determine shopping behaviour. A lot of this went into determining things like ranking (If someone searches "Tshirt" what shows up on the first page and in what order etc.)

Since we were only running search and not payment processing, the tracking pixel/API for "Add to Cart" was a big thing for us. The whole product ran on revenue-share so we were paid per X ATCs

Interesting to see if any of the customers were affected by bots doing ATC and how it was handled if it was.