[echelon]

> perhaps explicitly failing if `n` gets too big

That's the problem. A lot of these quadratic time algorithms don't set limits.

Even 'n!' is fine for small 'n'. Real production use cases don't have small 'n'.

[masklinn]

> Real production use cases don't have small 'n'.

Real production use cases absolutely have small n. You don't hear about them, because it's very hard for them to cause issues. Unless the use case changes and now the n is not small anymore and nobody noticed the trap.

[lassejansen]

Or, phrased differently, if n has an upper limit, the algorithm is O(1).

[connicpu]

As long as you have tests that regularly exercise your algorithm at n=max where you would notice if they were exceptionally slow

[haiku2077]

I have an app that's been running an O n^2 algorithm in "production" (free open source app used by various communities) for about half a year now.

It's been fine because "n" is "number of aircraft flying in this flight simulator" - and the simulator's engine starts to fail above around 2000 anyway. So even in the worst case it's still going to run within milliseconds.