21:30, sysadmin, chatting with my colleagues, when one posts a screenshot of a message he just received from a dev :
"Hello, sorry for bothering you this late but we have a demo tomorrow morning and the app is completely stalled. It fails with the message 'cannot write to <file>, no space left on device'"

I say "I bet that they somehow managed to make their DB grow uncontrollably".

Colleague asks which server hosts the app, Dev answers "one of ours", then adds after a few seconds "wait, do you need the IP of the server? Dev2 should be able to provide it", before finally adding "we use a scheme in <other project> DB actually".

Finally, Dev2 declares that the bug is solved: "There was a loop that caused a DB view to grow constantly and it filled the filesystem".

Me: "Called it".

They cleaned the view: 41GB freed.