Monzo SE III in London: CV deep dive, a Java web crawler take-home and a top N songs system design

Internal Recruiter

First was a typical recruiter screen with some general questions on my background, asked me why I wanted to join Monzo, and then gave me a brief background on the company mission which was all very straightforward.

Initial Call

After that I had a 1hr session with one of their devs where I was asked to talk through my CV and go deep on some of my past work projects. Seemed like they were mainly checking if I could explain my decision making, tradeoffs, and what was challenging about the project. For this I'd say you really want to know your CV inside out and come prepared with a project to talk about, discuss design decisions, what would you do differently looking back on it.

Take Home

Next round was a choice between a take home assignment or a paired programming task. I chose the take home and it was to build a web crawler in Java. They let me pick the language for it. Told me to make sure you include a README where you explain your decisions. Then they scheduled a follow up review call walking through your code. I'd say if you're using AI assistance you'll get tripped up here, they want you to justify your decision making and asked me questions on the data structure tradeoffs, DB indexing, and some questions on concurrency and how I'd handle duplicate URLs.

System Design

After the take home was system design whiteboarding with Excalidraw. I was asked how would you implement a top N songs getting played right now endpoint for an app like Spotify, and they specified users would be in the millions. I remember they asked me about latency issues as they wanted me to explain my caching strategy in more detail (I used Redis sorted sets).

Behavioural

Final round was a behavioural call with 2 devs which was standard again. They asked about communication, examples of times I communicated well and poorly, and how I work in a team. Most questions I had an answer prepared for, made sure I used the STAR method for each wherever I could.