Ask HN: What is the most impactful thing you've built?

My software consultancy developed a surveying system for young people suffering with mental health issues. It was used before their sessions with medical professionals, and helped inform their clinician on their current state, along with overlaying data from previous sessions to help point out patterns and possible risks.

We met with focus groups of young people (and separately, clinicians) in developing the app, and I felt a strong affinity for the entire project. It still gets used thousands of times per day, and I'm glad I could help bring it to life.

I'd always loved building software, but this project showed me it's so much more than technology.

When the big earthquake in Nepal happened in 2015, I was working with a volunteer organization called Translators Without Borders to help with translation during relief efforts. Since I was in the USA I could not contribute back physically, so this was the next best thing.

My goal was to help volunteers that were in the field in Nepal communicate in English -> Nepali and back. Even though this was somewhat effective, there was still a communication gap because most people in Nepal in remote parts could not even read in Nepali.

I looked around for solutions but couldn't find any Nepali Text To Speech solutions. The builder brain in me fired up and I decided to build a Nepali Text To Speech engine using some of the groundwork that was laid by Madan Puraskar Pustakalaya (Big Library in Nepal) which they had abandoned halfway.

I spend all night hacking along to build a web app that let the volunteers paste translated text and have it spoken. The result was https://nepalispeech.com/ and the first iteration of this was built in just 13 ish hours.

I hope the people that got affected by the earthquake are in a better situation now.

I built the first "post-play" experience for Netflix. It made it so that Netflix would automatically start playing the next episode of the show you are watching after a 15 second count down. We built it in the Silverlight player on the web because it was the fastest way to A/B test new features at the time.

Before post-play, you had to open the episode menu and click on the next episode to play it. We didn't want to do autoplay for a long time because we were afraid people would fall asleep with Netflix playing and it would break the internet. So we included the now infamous "Are you still there?" popup a few minutes into episode 3 with no interaction with the player.

Now it is everywhere - YouTube, Hulu, HBO, etc. And people watch way more TV than they should.

This probably isn't that impactful on the grand scale, but I want to mention 2 things

On a problem meeting to get better at detecting some SMS fraud, we realized some manual labor the fraud team had to do with Excel. I made a program that automated the checks and presented a resulting ranked list, I saved that team (according to them) around 1 hour a day of boring, stupid work and let them either rest or use that time for better work

I did a small audit on webpage size on my company to see how impactful the changes would be. Approximately 30% to 40% of the page could be reduced. The calculated cost saved was low, $150 to $200 per month, but also around 100kg to 150kg of CO2 released on the atmosphere. If replicated on other pages the total cost saved on both dollars and CO2 could be tripled

While not a lot, I like to think that those small things done everywhere could ne a substantial help on global warming

I designed and implemented the whole graphic system for the World Cup '98 (working 100h weeks for months). Billions of people have watched in real-time the result of my work and I earned absolutely nothing from it :) (there's a fun story to write about this, the tremendous amount of work, setting up the WAN connecting the SGI machines together, building the remote control hardware, etc).