I’m Monzo’s Head of Engineering. A lot of the technologies mentioned above for us are accurate but some aren’t in use - notably PostgreSQL - and some others which are crucial are missing - eg. Kubernetes. The vast majority of the platform runs on AWS. Our engineering team has grown to around 60 now.
Our entire backend has been built in-house using modern tech. You can read a bit more about it on our blog if you’re interested: https://monzo.com/blog/2016/09/19/building-a-modern-bank-bac...