Monzo Backend Engineer interview guide
Monzo's backend engineering interview: the initial call, take-home or pair coding, system design and behavioural rounds.
About Monzo
Monzo is a UK digital bank. In the year to March 2026 it grew to 15.2 million customers and 10.4 million monthly active users, with revenue up 39% to £1.7bn and adjusted profit before tax up 20% to £172.6m. About half of its active customers use Monzo as their main bank.2, 3
The interview process
As described by one of Monzo's principal engineers in 2025.1
- Recruiter call
A recruiter gets to know you and explains the role and Monzo's mission.
- Initial call1 hour
A conversation with engineers, possibly future teammates, about your background and technical depth: a big technical challenge you've overcome, customer-facing systems, data structures, language choices, performance and reliability trade-offs, and security.
- Coding: take-home or pairing
You choose.
- Take-home. Done in your own time and IDE, in any language, followed by a review call. Include a README explaining the structure, how to run it and the trade-offs you made.
- Pair coding (45 min). Live with a Monzo engineer in Go, Python, Java or others, with unit tests provided. Practical problems only: "We're not going to ask you to invert a binary tree." You can use documentation.
- Systems design
A collaborative design session on a tool like Excalidraw, testing how you build scalable, reliable and fault-tolerant systems. Expect your interviewer to challenge assumptions and add new information that changes your design.
- Behavioural1 hour
Two engineers or engineering managers ask about teamwork, communication, learning and delivering large goals incrementally.
- Decision
A hiring committee reviews all the feedback and discusses your strengths and development areas.
What Monzo looks for
- First-principles thinking. Reasoning through a problem rather than reciting memorised answers.
- Trade-offs. Performance, consistency and availability, explained clearly.
- Your own contribution. "We're interviewing you, not your current or past team."
- Delivery at scale. Working with others to hit large goals step by step.1
Questions to expect
Based on the topics Monzo says each stage covers.
Initial call
Tell me about a big technical challenge you've overcome.
Tell me about a performance or reliability trade-off you made. Would you make the same call today?
Systems design
Design a system that notifies customers the moment their card is used.
Your design now has to survive one data centre going down. What changes?
Behavioural
Tell me about a large project you delivered in small steps.
Tell me about a time you learned something quickly to unblock your team.
How to prepare
- Pick the language you know best. Monzo wants idiomatic code, not a language you think they'd prefer.
- Write the README. For the take-home, explain the structure, how to run it and the trade-offs.
- Design out loud. Talk through data flow and trade-offs as you draw, and expect curveballs.
- Prepare "I" stories. Your own decisions and impact, not the team's.
- Use AI to prepare, not during. AI is fine for preparation, but not allowed in the interviews.1
Quick answers
Do I need to know Go for a Monzo backend interview?
No. The take-home can be in any language, and pair coding is offered in Go, Python, Java and others.
Does Monzo ask LeetCode-style questions?
No. Monzo says: "We're not going to ask you to invert a binary tree." The coding is practical and job-relevant.
Can I use AI in a Monzo interview?
You can use it to prepare, but not during the interviews.
Who makes the hiring decision?
A hiring committee that reviews all your interview feedback.1
Sources
- Demystifying the Backend Engineering interview processMonzo blog · 1 Mar 2025
- Monzo Annual Report 2026: Year in reviewMonzo · 19 May 2026
- Monzo reports revenue and profits leapTech.eu · 19 May 2026
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