I'm a developer in a quant role, and basically every job I've looked at in this market has similar requirements. See my other comment in this thread about the absurd support burden at XTX markets.
I was at Man AHL for 5 years after leaving GR and that is a pretty laid back company in comparison. I was not on a trade critical team per se, but some of our system were used for pre-flight checks. As such, if there was an issue the on call person got called at 5 am to sort it out. If not resolved within an hour or so, the cio/cro got called and had to decide whether to trade regardless or not. Thankfully not a common issue but definitely at least a call or two every time you did support.
I was at Man AHL for 5 years after leaving GR and that is a pretty laid back company in comparison. I was not on a trade critical team per se, but some of our system were used for pre-flight checks. As such, if there was an issue the on call person got called at 5 am to sort it out. If not resolved within an hour or so, the cio/cro got called and had to decide whether to trade regardless or not. Thankfully not a common issue but definitely at least a call or two every time you did support.