What's the most expensive infrastructure lesson you've learned the hard way?
Learned this one the painful way.
Heroku rotates DATABASE_URL during certain maintenance events.
If you've hardcoded that value anywhere instead of reading it from the environment, your app can randomly stop talking to the database after maintenance.
Nothing's "broken."
Your code is.
It's one of those infrastructure gotchas you only learn after losing a few hours debugging.
What's the most expensive infrastructure lesson you've learned the hard way?
Mine was this.
What's yours?