The key is 100% boycotting all services provided by a company. Wikipedia’s list of Amazon product/services as reference (https://en.wikipedia.org/wiki/List_of_Amazon_products_and_services).
Incidentally, I know entire neighborhoods that don’t have other grocery stores besides Target/Whole Foods, not to mention that AWS is the cloud computing industry standard… As a personal example, my vet-prescribed cat foods are manufactured by Purina, a subsidary of Nestlé (needless to say, a separate but also extremely evil large corporation)
A direct boycott of Amazon and its subsidiaries? Super easy, barely an inconvenience.
But boycotting services that happen to use Amazon? Impossible!
Any business may use products ordered from there. Your local toll gate may use AWS. Unless you are a major client nobody is going to let you audit their supply contracts.
Yeah, AWS is ginormous and largely invisible. You can usually figure out when something’s in AWS if you can traceroute it, and sometimes by IP, but that requires knowing the IP of the server in question AND having the know-how to use and understand those tools’ output.