What have you built that is so stable that you almost forgot about it?

One that I did forget about touching it (but use it daily): A monitoring system.

We have many at the company, but none of them did really cover a good overview of the KPIs that we did want.

Components: a few perl scripts, launched from a single sh script + nginx + letsencrypt

Basically it collects metrics from remote APIs and also from other internal monitoring systems, and generates static JSON files into /dev/shm/, which are served by nginx + letsencrypt from there.

The frontend is just a few vanilla HTML files, with vanilla javascript, dark theme, and mobile first responsive design (it's mostly tables to show KPIs). I'm a sysadmin, not a frontend designer, but everyone in the company (even the frontend team) likes it.

Built between 3 and 4 years ago, in two days, one week later I did adjust the logrotate rules for the vhost, and never touched again.

All the company looks at it daily (developers, support, infrastructure, even the CEO), +/- 80 users during office hours, and it's the first place I check, wherever I am with my phone, when we get any alert.

Other one that I really forgot about it, but did remember thinking about this topic: A service to adjust kafka retention

It collects our kafka servers disk space for all kafka-logs volumes, we use replica 3, so it has some logic to make a decision, if the retention needs to be reduced or can be increased, has some up and low limits for the retention for each topic and a default for undefined topics...

Before having it, we did need to adjust/restore the kafka retention almost daily, and check everything by hand.

Developed in one day, did forget about it until today.

I wrote a monitoring system for a Water Meter Calibration facility back in 1990. They contacted me in about 2008 to help get it running again after some hardware was replaced, and it wouldn't work. It turns out they had the two parallel cables swapped. As far as I know, that MS-DOS Turbo Pascal code, with built-in multitasking, is still in use, quietly doing it's job as a Man-Machine Interface.

I very much like the absolute lack of responses to this question.

The website of my apps is fully automated. I made my own Webview/JS to build my apps easily, and can create new apps with a template. This has been my best source of passive income for years, and I just remember it once a year due to namecheap invoice.

I didn’t build it but running pi-hole on a Raspberry Pi is a very seamless experience. Besides manually updating block lists I never had to ssh or login into the dashboard because of any issues—it just work.

A Telegram bot I made for personal tracking. It serves a single purpose, whenever I send it a command, it logs the current timestamp to a Firebase DB. The bot itself is hosted on a free Heroku dyno. It has collected over 850 timestamps across 3+ years and I haven't had to check up on it once.

A small webapp for a local non profit. Does its job, but doesn't really need anyone but some members of the non profit to log in. (The URL isn't currently publicized)

So I block all foreign country IPs, have a pretty good lockdown on open ports, and check for updates every now and then.

Visual Basic 6.0 CRM that uses .txt for every customer record.