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Comments (46)
- danpalmerI can't help but think this isn't the best idea, it raises so many questions. How does fail over work (it failed for me!), can you safely fail over, how does product think about the stack, is it funded well enough, how do you scale a system from zero to all traffic instantly, how do you effectively keep this environment warm, how do you determine which services are critical enough to be in it, how do you manage finding the bugs in two separate stacks, and so on and on and on.It seems like it would be better to invest in a platform that is distributed across multiple failure domains. Some companies call this a cell architecture. For Monzo this might mean true multi cloud, but they already have bare metal services for bank integrations so they are already hybrid in some respects.It's not the decision I would have made, and I'm not sure I agree with their reasoning, but I'll also admit that I have not run a bank, I don't know all their constraints, and there are some good tech folks at Monzo. That said, I am an SRE at Google so I'd like to think I'm not completely naïve here.Edit: after reading in more detail I'm puzzled. The justification for Stand-In and not traditional scale-out is the difficulty of data consistency (agreed!), but then Stand-In is just eventually consistent anyway, and introduces sync problems in both directions. Admittedly I'm spoilt by Spanner, but I do wonder if Monzo is being bitten by past architecture choices here.
- janpeukerMinor thing but I do like they use the word "Stand In" here in the payments / financial sense of Stand-in processing (STIP), which is usually used when a bank is offline to keep essential services such as public transport working.
- jmkniJust pointing out this is from February 2025, so has been a thing for a while
- sdcfgyDue to the recent outage where it didn’t work properly, this should be renamed Monzo Limp-In.
- tarun_anandI think this is what distributed systems has a phrase for: "graceful degradation".
- qmarchiSomething like this has been top-of-mind for us since we have a heavy reliance on AWS, which was made evident with the VPC Origin failure earlier this year.Multi-cloud is best cloud.
- varispeed> Monzo Stand-in is an independent set of systems that run on Google Cloud Platform (GCP)Given the US Cloud Act, how Monzo is protecting customers' financial data from being accessed by foreign government without Monzo's knowledge?Everyone does it, does not excuse it.Also shows lack of faith in British business.
- ValodimAlmost seems like they can do anything at monzo.com
- ascorbic[2025]
- greatgibThere are 3 things I have in mind when reading this:- it should be so frustrating for a dev to work on a full core banking that is mostly useless and userless except maybe 1h every 3 years.- if you build a totally different implementation to handle high traffic transaction from third parties that don't operate for days or months, i would expect it to be fragile. Like for example suddenly you receive unicode special chars that you didn't expect in labels and boom.- last, I think that in most incident cases, the situation is not clear enough to be able to switch to the full different system. Rarely it will be your whole infra but part of it, so there is always the question to what to do in such a case, or if your main infra goes crazy with loops for example, or if you lose control because of a network, aws, infrastructure issue thr problem might be that you have no visibility on what is working and what is not, not necessarily the control to stop the faulty services, etc...
- guiriduroBy using another US hyperscaler for your backup platform you're still unhedged against US governance failure/breakdown.
- IshKebabMonzo is great. Rare example of a consumer banking company that makes things easy. I just signed up for their phone service in literally 3 minutes. Didn't even need to talk to anyone to port my old number. I'm going to move all my ISAs and SIPP to them next I think.
- syou1024[flagged]