You know how HTTP GET requests are meant to be idempotent?
When I recently added 'click to unsubscribe' functionality to my emails, the URL got wrote out into some logs. Those logs got written to a Slack channel and Slack loves to click any link it sees. Oh, and it doesn't respect robots.txt.<p>But all I saw was every member of my list clicking 'unsubscribe'. It took a good hour to figure out exactly what was going on.<p>Idempotence is not the problem here, by the way. That just means calling the method twice has the same effect. But GET should have no side-effect, in an ideal world. Of course, in the case of unsubscribe links, it needs to have a side-effect to comply with the law.