Tolerating full cloud outages with Monzo Stand-in

[QuinnyPig]

What I wonder is “have they isolated third party dependencies?” If AWS is hard down, those may well be impacted—in some cases, by their own third party dependencies. You can test turning off your AWS environment, but you can’t really test turning off S3 for everyone…

[abritishguy]

It's a very good question. The stand-in system itself has been built to have basically no external dependencies itself.

So, the question you are really asking is "to what extent are the other parties involved in the processing of payments resilient to AWS failure" – e.g. Stripe probably isn't and that's probably a decent chunk of e-commerce.

I definitely don't think this would be anything close to smooth sailing if AWS was to fully go down, but we do have the benefit that underlying payment infra is still dominated by on-prem with leased lines etc. My best guess of the actual behaviour would be that bank transfers would keep working, the card networks themselves would keep working but the average e-commerce website would not.

Naturally, we can only control for what we can control for – and for us the primary benefit of stand-in is what it gives us in the much more likely scenario of an incident in our platform.

[sleepgou]

From what I understand of payment systems this is so that payments through card machines, contactless payments for public transport, cash withdrawals from ATMs, etc. all continue to work. A lot of those systems are surprisingly insulated from AWS simply by virtue of being extremely archaic

[Koffiepoeder]

Unrelated tangent: I was reading the article and suddenly realised that I could not identify the font. After a quick search:

> Our functional typeface is Monzo Sans, a custom cut of Universal Sans, meaning it’s unique to Monzo. We chose it for maximum readability, with generous dots and curled ends.

Intersting choice, but I dig it :)

[noodlesUK]

This seems especially relevant given the massive outage that Barclays, another major UK bank just suffered. Barclays was down for around two days with customers unable to spend money at all.

I suppose had they implemented a similar system, they would have degraded into a minimum viable banking system rather than the total outage that impacted so many brits.

[mmikeff]

On the last day that tax payments were due

[tikkabhuna]

These blog posts are why I continue to support Monzo. Their openness is really appreciated.

[theginger]

A decent setup which allows you to prove you are not dependent on 1 cloud provider will probably pay for itself when it's time to negotiate discounts.

[cbg0]

I doubt the sales folks you'll be talking to will care about your multi cloud deployment, as they don't have the skills to verify something like that.

[paulbjensen]

My only conclusion is that Monzo would rather embrace the apocalypse than rely on Microsoft Azure to provide a tertiary fallback.

[matt-p]

Who can blame them. Me too.

[4ndrewl]

Really interesting. Would love to understand how they came to the decision to build this,and whether there's any precedent for it.

[matt-p]

Part of being a regulated bank in the UK is proving infrastructure resiliency.

Monzo were the first bank here to run entirely on the cloud, so I imagine the regulators were extra strict with them.

I'm not saying this level of resilience is due to that alone, but perhaps it started them on the path?

[quesera]

Payment card networks have delegated authorization plans, where if a major processor goes down, they will still route transactions and use a simplified secondary network for making approval decisions.

It's called "stand-in processing", and I assume it's the inspiration here.

[joshstrange]

Completely unrelated to this blog post but I really dislike Fintech saying "Get paid early" in their promos.

It's clearly marketing at someone too stupid to be able to see right through how utterly useless that is. If you are celebrating getting your paycheck 1 day earlier (every time) then your financial literally and financial health are probably in the toilet. They _must_ know they are preying on people with statements like that.

Then again, 90% of Fintech seems to be just a heavy layer of lipstick over an archaic system. Often with very little care of if any of the tools actually help people and more of a focus on how flashy or how much people think they are being helped.

[jkingsman]

Though, in some cases (like when it's your bank saying it), it's usually just them frontrunning reliable (coming from a payroll provider) and predictable (getting paid the same time each month) ACH transactions with a near-zero likelihood of not settling, then crediting you the money before the ACH is totally settled, so not ALL cases are fintech gimmicks.

But most are, and unfortunately, as the proliferation of payday loans shows us, there is no shortage of desperate people and organizations willing to take advantage of that.