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How to Pass the October Software Engineer Interview in 2026

Growth · Software Engineer Interview Guide

Interview language: English

The October DNA (TL;DR)

October's 'Functional Always' principle underpins the evaluation, seeking candidates who demonstrate a deep understanding of financial product mechanics and can articulate how their work contributes to robust, scalable solutions for October Europe Access. They grade for practical application over theoretical knowledge.

The October Interview Loop

Your onsite loop will typically consist of 5 rounds.

1
Round 1
Recruiter Screen
Motivation, role fit, logistics.
2
Round 2
Coding Screen
LeetCode-medium algorithmic problems under time pressure.
3
Round 3
System Design
Distributed systems, trade-offs at scale, architecture under constraints.
4
Round 4
Onsite Coding
LeetCode-hard problems, reasoning about defects, code clarity, edge cases.
5
Round 5
Behavioral / Leadership
Past evidence of ownership, influence, resolving conflict.

The Danger Zone: Top Reasons Candidates Fail

Based on our database of October interview outcomes, avoid these common traps:

Providing a resolution that ignored the long-term maintainability of the codebase
Using incorrect formulas for monthly payment calculation (e.g., APR vs. monthly rate).
Overlooking the real-time requirement and proposing batch processing.
Failing to mention the specific financial data consistency constraints involved

Test Yourself: Real October Questions

Three real prompts pulled from our database.

Type · algorithmic

Given a list of loan applications, each with an amount, interest rate, and a submission timestamp, write a function to calculate the total approved loan amount for a given day, considering that applications are approved sequentially and a loan is only approved if its amount is less than or equal to the remaining available capital for that day. Assume a fixed daily capital pool.

Type · past-experience

Describe a complex bug you encountered in a production system. Walk me through your process of diagnosing and fixing it, and what steps you took to prevent similar issues in the future.

Type · coding

Write a function to simulate loan amortization. Given a principal amount, annual interest rate, and loan term (in years), calculate and return the monthly payment and generate an amortization schedule showing the principal and interest paid each month, and the remaining balance.

+ many more questions, signals, and worked examples

Unlock the October rubric, free

October Interview Question Bank

A sample from our database, grouped by round. Sign up to see the full set.

9 of 12 questions shown

Recruiter Screen

1
Type · motivation
Why are you interested in joining October, a fintech company focused on SME lending, compared to other opportunities in the tech industry?

Coding Screen

2
Type · algorithmic
Given a list of loan applications, each with an amount, interest rate, and a submission timestamp, write a function to calculate the total approved loan amount for a given day, considering that applications are approved sequentially and a loan is only approved if its amount is less than or equal to the remaining available capital for that day. Assume a fixed daily capital pool.
3
Type · algorithmic
Implement a function that takes a list of transactions (each with a user ID, amount, and timestamp) and returns the top K users with the highest net transaction volume within a specified time window. Handle potential ties.

System Design

4
Type · design
Design a system to automatically detect and flag potentially fraudulent loan applications in real-time. Consider data sources, processing pipeline, fraud detection models, and alerting mechanisms.
5
Type · design
Design a microservice responsible for calculating credit scores for loan applicants. Consider the data inputs, the scoring algorithm's complexity, potential external dependencies (e.g., credit bureaus), and how to ensure low latency and high availability.
+ 1 more questions in this round (sign up to unlock)

Onsite Coding

6
Type · algorithmic
Implement a rate limiter for API requests to prevent abuse. The rate limiter should allow a maximum of N requests per user within a M-minute window. Consider different strategies (e.g., token bucket, leaky bucket) and discuss their trade-offs.
7
Type · coding
Write a function to simulate loan amortization. Given a principal amount, annual interest rate, and loan term (in years), calculate and return the monthly payment and generate an amortization schedule showing the principal and interest paid each month, and the remaining balance.
+ 1 more questions in this round (sign up to unlock)

Behavioral / Leadership

8
Type · past-experience
Tell me about a time you had to make a significant technical decision with incomplete information or under pressure. How did you approach it, and what was the outcome?
9
Type · past-experience
Describe a complex bug you encountered in a production system. Walk me through your process of diagnosing and fixing it, and what steps you took to prevent similar issues in the future.
+ 1 more questions in this round (sign up to unlock)

Unlock all 12 October questions, free

No credit card. Every question with its framework, the grading signals interviewers score against, and a worked answer for each.

Unlock all 12 October questions

Interview tracks at October

How October's DNA translates across functions. Pick your role.

See Software Engineer salaries by country

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Practice October interviews end-to-end

October Mock Interview

Run a live mock interview with our AI interviewer using October-style prompts. Get scored on structure, signal, and answer length - exactly how the real loop grades you.

Open

STAR Stories for October Behavioral Rounds

Build a Story Bank of your past wins, mapped to the leadership signals October interviewers grade on. Reuse them across every behavioral round.

Open

October Interview Prep Hub

The frameworks behind every October round: CIRCLES for product sense, hypothesis-driven debugging for analytical, STAR for behavioral. Learn each one in 10 minutes.

Open

Interview Frameworks

CIRCLES, STAR, AARRR, RICE, MECE. The exact frameworks that make October interviewers nod instead of frown. Step-by-step playbooks with the moves and the pitfalls.

Open

Sample answers

What a strong answer to these October interview questions shows.

A strong answer shows: Clear and efficient algorithm design.; Correct implementation of the approval logic and capital management.; Consideration of edge cases and input validation..

Describe a complex bug you encountered in a production system. Walk me through your process of diagnosing and fixing it, and what steps you took to prevent similar issues in the future.

A strong answer shows: Detailed explanation of the bug and its impact.; Clear, step-by-step description of the debugging process.; Effective and specific preventative measures implemented.; Understanding of production system stability..

Frequently asked questions

How long does the October interview process take?

Most candidates spend between 4 and 8 weeks from recruiter screen to offer. The onsite loop itself runs in a single day or is split across two half-days, with debrief and offer typically within 5 business days after.

How should I prepare specifically for October?

Focus on three things: (1) the company DNA shown above - what they actually grade for, (2) the rounds in your loop, especially the round most candidates underestimate, and (3) drilling on the question types in this guide using a structured framework like CIRCLES or STAR.

Does this apply to engineering or design roles at October?

The DNA stays the same - what changes is the round mix. SWE candidates face coding screens instead of Product Sense; designers face portfolio reviews and design exercises. The "what they value" and behavioral signals carry across all functions.

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