New technical post!
Last year we worked on a project to bring our Faster Payments connection into Monzo. And our in-house gateway has been running since November 2019.
Backend engineer @watbe shares a detailed insight into how we actually went about building it – and he’s on hand to answer any questions too 
That’s a great breakdown of what is involved and the scale of it too!
I’ve been with Monzo since late 2018 and the innovation has been excellent. Having things in house means we control things. Why the hell would you want a legacy bank? Beats the hell out of me. 
The reasons are many and varied. And probably for another thread.
Understood! It’s a case of horses for courses. Monzo is a perfect fit for me not least because it cuts out the pompous crap that you often get elsewhere. But that’s just me.
Monzo does everything I want from my bank but of course I know that other people’s opinions differ from mine. Opinions which of course I respect.
Huh? I think you mean they control things not we.
Yes! Sorry typo.
All good. 
Maybe I missed it, but why did you have to use your own servers and not AWS for this?
I seem to remember that it’s because you need somewhere fixed in location to actually plug in the physical cables from Vocalink’s secure network and AWS does not really cater to that
That’s roughly it. I’ll keep things vague but you have to connect to many payment networks using physical direct connections.
If you have to have something relaying the messages anyway, why not take advantage of it to build some capacity and resilience at the edge?
Overall, I’ve been watching the progress of this project internally and it’s probably the shining example of what Monzo can do when we really get to write something from the ground up that most banks outsource or buy a product to achieve. 
Are there any other significant parts of Monzo’s infrastructure that are still outsourced?
Are there any other significant parts of Monzo"s infrastructure that are still outsourced?
In terms of payments, there are still some smaller schemes that depend on third parties. We make regular assessments to determine if and when it is beneficial to have a more direct integration.
I seem to remember that it’s because you need somewhere fixed in location to actually plug in the physical cables from Vocalink’s secure network and AWS does not really cater to that
Rika’s answered this well; there are requirements both in terms of private networking and benefits in terms of resilience.
Well described, thanks for such detailed information.
thanks Wayne for sharing, good overview of the challenges with payment gateways