Monzonaut AMA - Jon - Backend Engineer Borrowing 🧰

We’re back yet again :tada:

After a short intermission we’re going to continue picking the brain of the Monzo staff :brain:

This week we have @JonH who is one of our fantastic Backend Engineers who has very kindly offered to answer some questions. A little introduction from Jon below :point_down:

Hi everyone :wave:

I’m Jon and I’m an engineer in Monzo’s Borrowing team, which is where I’ve spent all of my 3+ years at Monzo.

Before Monzo I spent 5 years as a management consultant, flying around the world to build people spreadsheets, which looking back was a bit of an environmental nightmare :flushed:

Now I build systems to help people who have a Monzo borrowing product and then find themselves in financial difficulty. Most recently that’s meant supporting the launch of Monzo Flex, which I’m really excited about! :tada:

Feel free to get your questions in - Jon will be around until Friday 19th Nov :pray:


I realise this is incredibly over simplified, but more on this please!


What does a day of the week look like for you? :thinking:

Is there anything in your previous role you’d like to see at Monzo?

Hi Jon,

I have Monzo Flex, I want to pay some money off early, but the page is not loading to allow me to do so? Can you help please?

Hey @ClareHerbie :wave:

This might be a bit better answered by our team available through the in app chat service. Head to the Help section and you’ll be able to speak to someone there :blush:


What’s the biggest joy vs biggest frustration working with Open Banking?

How much of an impact (if any) does regulation slow down advancements in banking technology?

What feature which you have worked on, do you feel has made the biggest difference to Monzo customers across the globe?

Finally, more out of curiosity than anything else, have you dabbled much with Solidity and taken a look at some of the innovation going on with DeFi?

Could you expand on this also please?

Thinking out loud because I have no idea what goes on (and how stupid / narrow minded it probably sounds) I always assumed help and support was done through chat. Mainly with guidance and recommendations to use government backed services who help people with debt for example.

This is obviously for some of the more serious cases, beyond perhaps payment breaks and freezing interest I assume. Unless these are some of the tools you’re referring to :thinking:

Or are they tools for the customer rather than the specialists? Like gambling block for example.

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What’s the biggest outage you’ve caused ?

Who hasn’t if we are being honest :slightly_smiling_face:

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Far too many sensible questions…

Would you rather sneeze everytime someone said your name or get the hiccups everytime someone said hello? :thinking:

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Would you rather find mushed up banana every time you put your hand in your pocket or have your Mum see your full browser history once? (Sorted by most embarrassing, so she doesn’t miss anything good)

I’ll be answering these this afternoon – last call for any more!

(in reality I’m a soft touch; if you ask a question afterwards I’ll probably still answer it :sweat_smile: )


Wow, there’s a lot I could talk about here. Which bits are you most interested in @Revels?

I’ll assume the “building people spreadsheets” for a moment. This covered a lot of ground. Examples included:

  • modelling business decisions (“if we change the price of this product by this much, how much more/less profit do we think we’ll make based on <many inputs>?”)

  • automating processes – using Excel to pull data from a SQL database and build large slide decks for supplier negotiations

  • pretending an Excel spreadsheet was an app – making it pretty and interactive using VBA (:nauseated_face: )


It usually starts between 9 and 10am. I catch up with the rest of my squad at our daily check-in and then the day is usually some combination of:

  • other team meetings (e.g. retrospectives, where we reflect on what’s going well/could be improved with how the team works)

  • answering escalations from COps (customer support)

  • working together with other engineers in my team (“pairing”)

  • gathering requirements for upcoming work, and proposing how we might meet them

  • working on our current sprint goals (actually writing code!)

I’ve usually exhausted all my attention by about 5.30pm. Which is convenient, because that’s when I normally start my second job, doing dinner/bath/bed for our daughter! :bathtub:


I’ve actually messed up here! I need to leave for a bit, but will come back and answer your other questions once little one is asleep :sleeping: :crossed_fingers:


I haven’t done any work directly on Open Banking. I think the work our teams working on Monzo Plus and Premium are doing to integrate your other accounts in Monzo is ace. We also added the option recently to prove your income via Open Banking when applying for an overdraft, which I think is a great use – not everyone gets paid into Monzo! (yet :wink: )

My frustrations are the wider banking industry’s reluctance – and delay – in realising the potential. I suppose it’s not a good thing if you’re used to “owning” customers and making easy profits for decades (or centuries!) 🤷

I reckon the teams that work with it would probably complain about all the unhelpful acronyms – it’s the complete opposite of what we’re used to …

You can read more about Open Banking and how we use it at Monzo in our recent blog post.

Regulation is a really interesting topic. Does it slow down innovation? Probably. But I don’t think it’s a bad thing. Imagine if banking wasn’t regulated – I expect there’d be some more innovation, yes, but probably an awful lot of customer harm too :grimacing:

I haven’t directly worked on changes that affect large numbers of customers. But there are other ways to have impact. So I think the highest impact changes I’ve made were ones that sped up onboarding and productivity of other engineers.

When I started I was surprised how many commands I had to copy/paste into the terminal to get my laptop set up. You had to waiting for each one to complete before kicking off the next, and … it didn’t feel like a good use of my time. So I wrote a simple script to automatically run them all. And as far as I can tell, new engineers still use the same script 3.5 years later :exploding_head:

I have not :see_no_evil: – high on my to-do list is to go through Crypto Startup School which other, much more knowledgable, folk at Monzo recommend as a starting point :nerd_face:


Here’s an example of how a customer might engage with some of these tools if they find themselves struggling.

Each month on the 1st some customers don’t have enough money in their account to cover the interest from their overdraft usage the month just gone. The money you owe still gets collected, taking you beyond your overdraft limit. The first thing we do is send you an in-app prompt, asking you to add money and get back within your limit. You can self-serve some things, for example telling us that you’ll pay us back by a given date, e.g. when you next get paid. That stops us sending you any more messages during that time :zipper_mouth_face:

If things are more serious, you can always chat with us at this point. Typically we’ll ask you to fill out a budget assessment in your app, to help us (and you!) better understand your incomings and outgoings. It tells us what you might be able to afford to pay back over time. Here’s an example summary once you’ve answered all the questions

You might then agree to go onto a plan, where you’ll pay a certain amount into your account each month. Depending on how much you can afford, we might also stop charging interest at this point to help you pay back what you owe more quickly.

All of this requires internal tooling, to see someone’s borrowing with Monzo, review budget submissions, and set up or review plans!

This is just a snapshot. There’s lots more we do to ensure good customer outcomes. As you say, one important aspect is signposting customers to other support that’s available. We also have some of this information on our website.


The worst issue I’ve faced wasn’t an outage as such. Rather, we make a mistake with some of the wording in a message we sent to some customers, which took a lot of time and effort to make right :sweat_smile:


I’ll take the sneezing thanks. Hiccups can last for ages; a sneeze is over and done with!


Ah, the business end of proceedings.

I get really cold hands, so pockets are too useful to be filled with mushed up banana :ohno:

So I guess I’ll take my chances with the browser history. It’s pretty vanilla; I think the most likely upset would be finding out what she’s getting for Christmas! :gift: