Interview: Inside the mind of a Monzo engineer

Monzo prides itself on creating a bank that “lives on your smartphone”. IT is part of it’s DNA.

2018 may infamously serve as a period of IT meltdowns in banking. More and more, the tech function at banks is not only an innovative luxury but increasingly business critical.

To understand how the digital-first challenger keeps day to day mission critical systems running, bobsguide spoke to Monzo engineer Matt Heath.

Where do you fit into to Monzo?

I am an engineer. I’ve been at Monzo for two and a half years. I’ve been there right from the beginning. I’ve worn many different hats. At the moment, I have been working on the product teams for the last few months. We have cross functional teams, we have eight people focused on trying to make the product much nicer. Helping make sure it fits the requirements for a progressively larger group of people. And helps people from day to day.

So, it’s a little bit different. It’s a more generalised product team. We are making lots of small inch routive developments to the product so that people feel comfortable putting their salary in, or using us to pay their bills, making sure their bill payments are all reliable.

What’s happening right now at Monzo?

We are in the process of disabling the topping up feature of the app. We disabled it for new users a while ago, and we spent a long time testing that. Asking people how they felt about it, making sure that it wasn’t something that actually the majority of people used.

Typing in your card number to move money into your other account is not particularly user friendly. It would be far nicer if we could provide much better ways to do that just to make things much simpler.

Does the agile startup culture help with understanding the company as a whole?

I think it’s useful for people to move around over time so that they get exposed to a variety of different areas. In my time at monzo, right at the beginning we obviously spent some time building the prototype, we then developed the prepaid card, we built the start of the platform that that works on.

For a period of time after that I worked on the platform team, so that was doing a lot more specific infrasture from physical networking, we have a couple of physical locations, and then up through Amazon where basically all of our infrastructure runs and then the tooling on top of that which all of our other developers use.

In the last few months, I’ve been working on the product team and working on a lot of front facing customer systems. Having moved around and done those things I’ve been able to work on everything from product through payment systems, how various payment schemes work and that certainly helps me do my job better. I can give people context as we grow, as we onboard more engineers. I can help people get context.

As far as the team aspect, we think that it’s really important that each one of our squads is a small enough size that they can sit together and crucially has a range of skills that allows them to do their job.

In most product teams you would be looking at a mixture of IOS and android engineers, a number of backend engineers to actually build on top of the infrastructure that we have. We have a seperate platform team that builds the infrasture below that, and then a designer, and a product manager. They then integrate with other team who do user research and various other things. The aim there is to have a number of squads who are all independent, they have a goal, and they can quickly move and make adjustments to the product to get that done.

So it means that by empowering teams to make their own decisions they can move very fast. And then there is overriding communication between the product managers, and other members of the company who set the direction for them.

What aspects of AWS are you using?

We use quite a wide range of AWS tools. All of our applications that power the product which you see are on amazon. We use EC2 extensively – from EC2 instances, auto scaling groups, low balancing.

Would these services be considered critical to Monzo’s core systems?

No. And there is a definition of critical that the regulator defines. All of our infrastructure for payments, every interaction you have through the app, all of that is on Amazon. On a day to day basis, everything you interact with is from Amazon, but we then use a number of other providers. We use Google cloud for a handful of things, and a number of other third parties who help with the onboarding process.

How long has the relationship between AWS and Monzo existed?

Since day one, which was February 2015. It was before the FCA had issued their initial cloud guidance, which came a little bit later in the year. At that point we were going through the application process to become a bank. We took the route where you get the initial authorisation for the £50,000 limit, then you go into the mobilisation stage where you connect payment schemes, then prove that you can operate as a bank, and then your restrictions are lifted.

We knew upfront that would take a period of time, which is why we partnered with wirecard to build the prepaid card. That allowed us to build a very limited product, but we could get feedback from customers, and learn all about that space but without providing the full suite of banking functions.

We didn’t think it would be as popular as it was. We only had 3,000 cards printed originally, the alpha cards. Obviously, on day one you are forcing your family and friends to use this thing. It took off a bit more quickly than we planned, and then we had to do a huge round of Beta cards. We ended up a few hundred thousand people who used our prepaid card, which we have since moved over to our current account.

During that time, we were unsure if longterm if we would be able to run on a public cloud. For the initial prototype we could run on the cloud. We had a lot of experience across our team with Amazon. We went through the selection process, we built the initial versions on there but we built it in such a way that we knew if we needed to move off we could.

Can you still move off?

Yes, although I wouldn’t want to. It’s extremely important  both for us as a company, and also for regulation purposes that we can move off Amazon. It’s a regulatory requirement. Ultimately we work in a free market, Amazon provides an incredible level of service it makes it incredibly easy for us to move fast. We can grow really quickly, provide all the services we need. So, we have no incentive to move.

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