During Hurricane Maria most of Puerto Rico was offline. Slowly but surely, some people started having access to some online services. To this day, I don't know how, but I saw frequent posts in social media (Facebook and others) of people saying they could access spotty internet but SMS and making calls wasn't working, and asking people to let their family outside of Puerto Rico know that they were okay.
So I setup a site on glitch.com with real simple 2 field form. One for a phone number and another for a message to send. It was dead simple, no framework, no CSS, just little bits of vanilla HTML and JS, and a bit of backend code connected to Twilio. Some text on the top with instructions too. I was making it intentionally small so that a spotty connection wouldn't have a problem using it.
Any time I saw someone posting in social media asking for someone to reach out to their family, I posted a link. I also shared it in a slack where many from the PR diaspora where trying to contribute ways to help. Before I knew thousands of people were using it. I did some continuous monitoring to make sure nobody was using it for abuse, and making sure it was being used as intended. It would have been EXTREMELY easy for someone to abuse it if they wanted to.
No one abused it. Thousands used it as it was intended. Left it up for weeks, and I kept monitoring it to make sure it wasn't being abused. I eventually saw it had stopped being used entirely for two weeks and spun it down.
I saw some people posting about it afterwards being thankful they were able to receive messages from their family, and I'm happy I rushed through to write very sloppy high impact code.