No. You don't put yourself in that position that you need a fix at 4am. Roll back to a prior version, or shut the service down, or go into a reduced-functionality mode (e.g., readonly) as you can.

Give yourself time the next day to actually think about the problem with a clear head. At 4am trying to debug code, you're far more likely to cause more problems than fix things.

To me, I read this question the same as "Haskell's not useful when you're stuck in a well with a bomb ticking down." The language isn't the problem. It's the situation that's the problem.

Ok, I won't argue with that. If you don't work with mission critical systems -- sure, #1 doesn't apply to you. Play with any language you like.

Mission-critical systems use SRE principles so no one is debugging code at 4am. If you can't solve a production issue without looking at the source code, you'veong since failed at building a mission critical-system.

Even if your app is 100% bug free and fault-tolerant, sometimes an external system feeds it invalid data and you need to figure out how to contain and revert the damage. That was my last on-call involving reading a lot of code under time pressure (thankfully, not alone and not at 4 am).

All commenters who said "It's your own fault for writing crappy code, duh!" perhaps never worked with anything sufficiently complex and expensive.