One of the (legal ?) requirements we had to meet back in the 00s was that financial software (quant code, options trading) was "reproducible" for some length of time (7 years?). That meant: version control (SCCS, CVS, svn), archiving OS versions (SunOS, Solaris), and kit (Sun workstations and servers).
I have no idea if the last 2 ("OS", hardware) is even achievable in 2021. I can always get my source code from git, and possibly the 'configuration', but can I expect to run cloudy code in 7 years time?
I'd expect that if the cloud providers wish to acquire customers that have to comply with those regulations, the cloud providers will have clause in the contract that they are contractually obligated to keep the same services running for that period of time.
OS is reproducible with artifact repositories for OS and library packages. Hardware perhaps less so, but I guess a custom deal could be worked out with the right supplier. That, or go with emulation.
Emulation can technically have some frustrating difference quirks - which suggests a "stupid but works" source of consistency by using emulated environments from day one.
I can't testify to my statement being 100% true without a lot of tedious searching on the UK FSA/SFA/FCA/whatever they are now's website. But that's what I have a vague recollection of.
It's similar to HMRC's "we can come after you for unpaid tax for 7 years", but you can only go after the HMRC for 5 years for overpaid tax.
The rules are ultimately for the benefit of long term investigations such as the LIBOR rigging, and Guinness trials.
I have no idea if the last 2 ("OS", hardware) is even achievable in 2021. I can always get my source code from git, and possibly the 'configuration', but can I expect to run cloudy code in 7 years time?