I recently launched a product, called Thankbox.<p>Product idea is really simple - you can set up a Thankbox (like an online card) for someone and share it within your group of friends to put messages, images, gifs and cash in it. You then send it to the recipient.<p>We wanted to add a feature where the recipient could respond to everyone who had left messages on their card - a kind of "Thanks so much for your kind words" type thing.<p>We rolled it out to production. The first time it ran it <i>spammed everyone who had ever left a message on any thankbox with the response</i>. Luckily we just launched and we didn't have that many users.<p>I thought it'd be a learning experience worth sharing, though, so I wrote up a Twitter thread about it to share my embarassment as a learning experience.