Simply Business · Software Engineer
Updated · 2026-10-02

Simply Business Software Engineer
Interview Guide

THE 60-SECOND BRIEF

A Software Engineer at Simply Business plays a pivotal role in disrupting the traditional insurance industry by building scalable, reliable, and user-centric digital products. As one of the UK's and US's leading digital insurance brokers, the company relies heavily on its engineering team to simplify complex insurance processes for hundreds of thousands of small businesses. The systems you build and maintain directly impact how customers search for, purchase, and manage their insurance policies, making high system availability and clean integration critical to business success. In this role, you will contribute to a modern, service-oriented architecture that processes high transaction volumes daily. The engineering organization places a massive emphasis on modern agile practices, continuous integration and deployment (CI/CD), and robust testing.

This guide is scoped to a Software Engineer candidate at Simply Business.

Simply Business candidates report 4 rounds over 3-5 weeks. The stages below are what candidates describe, not a published process.

Pair ProgrammingRuby on RailsRuby Programming

24 min read

Browse Software Engineer questions

See the practice prompts

23Practice promptsAcross five skill areas

A Software Engineer at Simply Business plays a pivotal role in disrupting the traditional insurance industry by building scalable, reliable, and user-centric digital products. As one of the UK's and US's leading digital insurance brokers, the company relies heavily on its engineering team to simplify complex insurance processes for hundreds of thousands of small businesses. The systems you build and maintain directly impact how customers search for, purchase, and manage their insurance policies, making high system availability and clean integration critical to business success. In this role, you will contribute to a modern, service-oriented architecture that processes high transaction volumes daily. The engineering organization places a massive emphasis on modern agile practices, continuous integration and deployment (CI/CD), and robust testing. You will find yourself working within cross-functional teams alongside Product Managers, Site Reliability Engineers (SREs), and UX designers to iteratively deliver value. Rather than working in isolation, engineers here operate in a highly collaborative environment where pair programming is a standard, day-to-day practice. What makes this position both challenging and rewarding is the scale and complexity of the domain. You will be tasked with solving complex integration challenges with external insurance underwriters, optimizing high-performance APIs, and maintaining a codebase that is clean, modular, and maintainable.

01

Recruiter Phone Screen

reported

Initial discussion about your background, career motivations, and cultural alignment with the company.

What to demonstrate

  • Initial discussion about your background, career motivations, and cultural alignment with the company
  • Depth in Pair Programming

How to prepare

  • Be able to walk your CV end to end in two minutes, and say why this company specifically.
  • Have your salary expectations, notice period and location constraints ready, and ask for the rest of the loop in writing.
Simply Business Software Engineer candidate reports ↗
02

Technical Screening

reported

High-level technical discussion with a senior engineer focusing on past projects and technical philosophy.

What to demonstrate

  • High-level technical discussion with a senior engineer focusing on past projects and technical philosophy
  • Depth in Pair Programming

How to prepare

  • Answer aloud and timed: How does Ruby's garbage collection work, and how can you optimize memory usage in a Rails application?
  • Answer aloud and timed: Describe your experience with background job processing (e.g., Sidekiq) and how you handle job failures or retries.
Simply Business Software Engineer candidate reports ↗
03

Coding Assessment

reported

Practical coding exercise conducted over Zoom, working on a real-world coding problem.

What to demonstrate

  • Practical coding exercise conducted over Zoom, working on a real-world coding problem
  • Depth in Pair Programming

How to prepare

  • Answer aloud and timed: How do you approach testing in Ruby on Rails? What is your strategy for balancing unit, integration, and system tests?
  • Answer aloud and timed: Walk me through how you would design and write a logic layer for a hypothetical public-facing API.
Simply Business Software Engineer candidate reports ↗
04

On-site Interviews

reported

Intensive series of interviews covering system design, collaborative pair programming, and behavioral fit.

What to demonstrate

  • Intensive series of interviews covering system design, collaborative pair programming, and behavioral fit
  • Depth in Pair Programming

How to prepare

  • Answer aloud and timed: How would you diagnose and resolve a severe performance bottleneck or memory leak in a production application?
  • Answer aloud and timed: Describe a time you had to integrate a third-party service with strict SLA requirements. How did you build resilience into your integration layer?
Simply Business Software Engineer candidate reports ↗

PracHub editorial advice for the preparation topics above.

01

Embrace the Pairing Mindset

During any live coding or pairing session, remember that your communication is just as important as your code. Talk through your decisions, ask your partner for their input, and treat them as a true collaborator.

02

Structure Your Behavioral Answers

The culture-fit and behavioral rounds heavily utilize the STAR method. Ensure your answers clearly outline the Situation, Task, Action, and Result, and make sure to highlight collaborative efforts rather than just your individual contributions.

03

Prioritize Clean Code Over Speed

When coding, do not rush to finish the exercise. Write clean, modular code, follow TDD practices, and explain your architectural choices as you go. A partially completed exercise with immaculate code and tests is often viewed more favorably than a fully completed but messy solution.

04

Ask Thoughtful Questions

Use your time with Engineering Directors and Product Managers to ask deep, insightful questions about their roadmap, team dynamics, and how they handle technical debt. This demonstrates your product-mindedness and genuine interest in the role.

Choose a category, try a prompt, then open its approach, worked solution or follow-up when you need it.

16 technical prompts0 include a worked solution

How does Ruby's garbage collection work, and how can you optimize memory usage in a Rails application?

medium
Technical & Ruby on Rails Domain Questio

How does Ruby's garbage collection work, and how can you optimize memory usage in a Rails application?

Approach
  1. Say what the runtime actually does before reasoning about the code.
  2. Name what is shared across threads and what owns each piece of state.
  3. Identify the window where an invariant is briefly untrue.
  4. Distinguish a value from a reference to it, and say which one you handed out.
Follow-up
  • What happens if two callers reach this at the same time?
  • Where could this allocate more than you expect?

Track a rolling failure rate per destination for circuit decisions

easy
sliding windowring buffercircuit breaker

The egress service delivers about 1,500 webhooks per second across roughly 40,000 destinations, each call bounded by a 10 second timeout. Maintain, per destination, the failure rate over the trailing 60 seconds so a caller can ask before dispatch whether the circuit should open. Attempts arrive as (destination_id, finished_at_ms, outcome). Requirement: amortised O(1) per attempt, with total memory bounded by the destination count rather than by traffic. Give the structure, its exact memory, and the rule that stops a destination with three attempts from opening a circuit.

Approach
  1. Name the exact-deque version and then reject it as the default. Holding timestamps and advancing a tail pointer past anything older than now minus 60 seconds is a correct two-pointer window at amortised O(1) per attempt, but its memory tracks in-window traffic, so one destination in a retry storm holds hundreds of thousands of entries while thousands of quiet destinations hold none.
  2. Use a ring of 60 one-second buckets per destination, each bucket a pair of counters for attempts and failures. On an attempt, advance the ring by the elapsed whole seconds, zeroing at most min(elapsed, 60) buckets, then increment the head. That is amortised O(1) with a fixed footprint per destination.
  3. State the footprint: 60 buckets times two 4-byte counters is 480 bytes of payload per destination, so 40,000 destinations is roughly 20 to 25 MB with per-entry overhead, bounded by the catalogue rather than by the rate. The cost is granularity, since the oldest bucket ages out in whole seconds, which is far tighter than the decision needs.
  4. Require a minimum sample before the circuit may open. A destination with three attempts and three failures reads as 100 percent and is not evidence; a floor of roughly 20 attempts in the window makes the ratio meaningful, and below that floor use a run of consecutive failures as the trigger instead.
Follow-up
  • The fleet is 30 instances and each sees roughly a thirtieth of a destination's traffic. Where does the rate actually live, and what does a per-instance answer get wrong?
  • A destination answers in 9.5 seconds and succeeds. It is not failing but it is consuming your per-destination concurrency. What signal should open the circuit here?

Diff a projection against the primary without per-row point reads

hard
reconciliationrange hashingthrottling

The listing projection has drifted and some rows show a stale version. The primary holds 40,000,000 resource rows across 12,000 tenants while serving 1,200 writes and 14,000 reads per second. The obvious repair, reading each resource row and comparing its version against the projection, is correct and would eventually finish. Explain precisely why it is unacceptable here, then give a diff that finds the differing rows, state its complexity, and make it safe to run against a live primary. Replication lag is usually under 100 ms and is not bounded.

Approach
  1. Quantify the naive cost rather than calling it slow: 40,000,000 point reads at even 0.5 ms each is over five hours serialised, and the only lever is concurrency, which is exactly what you cannot spend. The primary's pool is sized for the write path, and 40,000,000 random reads evict the buffer cache that sustains the 85 percent cache hit rate, so the audit degrades the system it is auditing.
  2. Replace random access with one ordered pass per side. Both sides can be read in (tenant_id, resource_id) order, which is a sequential scan on each and a merge join in O(n) time and O(1) memory. For a dense diff that is the whole answer, and it reads the primary once instead of 40,000,000 times.
  3. For the expected sparse case, compare range hashes instead of rows: partition the key space, compute per range an order-independent aggregate over hash(resource_id, version), compare aggregates, and descend only into ranges that differ. With d differing rows and branching factor B, at most d ranges mismatch per level, so the drill-down examines O(d log_B(n/d)) ranges and reads full rows only in mismatching leaves.
  4. Aggregate with a sum modulo 2^64 or a multiset hash, never XOR. XOR is order-independent but self-cancelling, so two rows wrong in the same way, or a row duplicated on one side, leave the range aggregate matching and the range is declared clean.
Follow-up
  • The diff reports 900 stale rows. How do you decide between patching those rows and rebuilding the projection from resource_revision?
  • Same job, but the projection lives in a search index that cannot be scanned in key order. What changes?

Built from the rounds and topics Simply Business candidates report.

Small steps. Visible outcomes.0 / 7 completed
ONE WEEK · YOUR PACE

Prepare, practise & reflect

One practical outcome each day. Spend longer where you need it.

0 / 7 done
01Map the Simply Business loop
  • Write out the reported sequence: Recruiter Phone Screen, Technical Screening, Coding Assessment, On-site Interviews.
  • For each round, write one sentence on what it is judging, from the description above, and mark the one you are least ready for.

Deliverable: A one-page map of the 4 reported rounds, with the weakest marked.

02Work Pair Programming
  • Spend the session on Pair Programming, which Simply Business candidates report being tested on.
  • Write one worked example in Pair Programming and time yourself on it.

Deliverable: One timed worked example in Pair Programming.

03Work Ruby on Rails
  • Spend the session on Ruby on Rails, which Simply Business candidates report being tested on.
  • Write one worked example in Ruby on Rails and time yourself on it.

Deliverable: One timed worked example in Ruby on Rails.

04Work Ruby Programming
  • Spend the session on Ruby Programming, which Simply Business candidates report being tested on.
  • Write one worked example in Ruby Programming and time yourself on it.

Deliverable: One timed worked example in Ruby Programming.

05Answer out loud: Technical & Ruby on Rails Domain Questions
  • Answer aloud, timed: Explain how ActiveRecord handles database migrations and how you would prevent locking large tables in production.
  • Answer aloud, timed: What are the differences between blocks, procs, and lambdas in Ruby?

Deliverable: Spoken answers to 2 reported Technical & Ruby on Rails Domain Questions question(s), under time.

06Answer out loud: Practical Coding & System Architecture
  • Answer aloud, timed: Walk me through how you would design and write a logic layer for a hypothetical public-facing API.
  • Answer aloud, timed: How would you diagnose and resolve a severe performance bottleneck or memory leak in a production application?

Deliverable: Spoken answers to 2 reported Practical Coding & System Architecture question(s), under time.

07Answer out loud: Behavioral & Collaboration (STAR Method)
  • Answer aloud, timed: Tell me about a time you had to work closely with a colleague to solve a complex technical problem. How did you divide the work?
  • Answer aloud, timed: Describe a situation where you disagreed with a technical decision made by a senior engineer or architect. How did you resolve the disagreement?

Deliverable: Spoken answers to 2 reported Behavioral & Collaboration (STAR Method) question(s), under time.

Expand any day for tasks and deliverables. Your progress is saved on this device.

Behavioural rounds judge the decision you made and what it cost.

Describe your experience with background job processing (e.g., Sidekiq) and how you handle job failures or ret

medium
Technical & Ruby on Rails Domain Questio

Describe your experience with background job processing (e.g., Sidekiq) and how you handle job failures or retries.

Approach
  1. Pick a story where you made the decision, not one where you watched it.
  2. State the situation in two sentences and spend the rest on the reasoning.
  3. Give the blast radius: what could have broken, and what you measured.
  4. Name the disagreement and how you resolved it with evidence.
Follow-up
  • What would you do differently if you ran that again?
  • How did you know your change caused the improvement?

Tell me about a time you had to work closely with a colleague to solve a complex technical problem. How did yo

medium
Behavioral & Collaboration (STAR Method)

Tell me about a time you had to work closely with a colleague to solve a complex technical problem. How did you divide the work?

Approach
  1. Pick a story where you made the decision, not one where you watched it.
  2. State the situation in two sentences and spend the rest on the reasoning.
  3. Give the blast radius: what could have broken, and what you measured.
  4. Name the disagreement and how you resolved it with evidence.
Follow-up
  • What would you do differently if you ran that again?
  • How did you know your change caused the improvement?

Describe a situation where you disagreed with a technical decision made by a senior engineer or architect. How

medium
Behavioral & Collaboration (STAR Method)

Describe a situation where you disagreed with a technical decision made by a senior engineer or architect. How did you resolve the disagreement?

Approach
  1. Pick a story where you made the decision, not one where you watched it.
  2. State the situation in two sentences and spend the rest on the reasoning.
  3. Give the blast radius: what could have broken, and what you measured.
  4. Name the disagreement and how you resolved it with evidence.
Follow-up
  • What would you do differently if you ran that again?
  • How did you know your change caused the improvement?

Give an example of a project where you had to balance technical debt with the delivery of a new business featu

medium
Behavioral & Collaboration (STAR Method)

Give an example of a project where you had to balance technical debt with the delivery of a new business feature. How did you negotiate the scope?

Approach
  1. Pick a story where you made the decision, not one where you watched it.
  2. State the situation in two sentences and spend the rest on the reasoning.
  3. Give the blast radius: what could have broken, and what you measured.
  4. Name the disagreement and how you resolved it with evidence.
Follow-up
  • What would you do differently if you ran that again?
  • How did you know your change caused the improvement?

Tell me about a time you had to support or mentor a junior developer. How did you approach their growth and fe

medium
Behavioral & Collaboration (STAR Method)

Tell me about a time you had to support or mentor a junior developer. How did you approach their growth and feedback?

Approach
  1. Pick a story where you made the decision, not one where you watched it.
  2. State the situation in two sentences and spend the rest on the reasoning.
  3. Give the blast radius: what could have broken, and what you measured.
  4. Name the disagreement and how you resolved it with evidence.
Follow-up
  • What would you do differently if you ran that again?
  • How did you know your change caused the improvement?

Describe a time when a project you were working on failed or missed its deadline. What did you learn, and how

medium
Behavioral & Collaboration (STAR Method)

Describe a time when a project you were working on failed or missed its deadline. What did you learn, and how did you communicate this to stakeholders?

Approach
  1. Pick a story where you made the decision, not one where you watched it.
  2. State the situation in two sentences and spend the rest on the reasoning.
  3. Give the blast radius: what could have broken, and what you measured.
  4. Name the disagreement and how you resolved it with evidence.
Follow-up
  • What would you do differently if you ran that again?
  • How did you know your change caused the improvement?

Describe a time when you identified a user pain point and proposed a technical solution that directly improved

medium
Product & Strategy Alignment

Describe a time when you identified a user pain point and proposed a technical solution that directly improved the user experience.

Approach
  1. Pick a story where you made the decision, not one where you watched it.
  2. State the situation in two sentences and spend the rest on the reasoning.
  3. Give the blast radius: what could have broken, and what you measured.
  4. Name the disagreement and how you resolved it with evidence.
Follow-up
  • What would you do differently if you ran that again?
  • How did you know your change caused the improvement?
  • 01

    Describe your experience with background job processing (e.g., Sidekiq) and how you handle job failures or retries.

  • 02

    Tell me about a time you had to work closely with a colleague to solve a complex technical problem. How did you divide the work?

  • 03

    Describe a situation where you disagreed with a technical decision made by a senior engineer or architect. How did you resolve the disagreement?

  • 04

    Give an example of a project where you had to balance technical debt with the delivery of a new business feature. How did you negotiate the scope?

PracHub preparation framework ↗
How technical is the recruiter screen at Simply Business?

The initial recruiter screen is very light and conversational. It focuses primarily on your background, your career motivations, and your alignment with the company's culture. However, because Ruby on Rails is a strict requirement for most engineering teams, the recruiter will verify your hands-on experience with Ruby during this call.

Simply Business Software Engineer candidate reports ↗
What is the pair programming interview like?

The pair programming session is designed to feel like a normal day-to-day work session. You will work with a senior engineer on a practical coding task, such as refactoring an existing piece of code or implementing a basic logic layer. The interviewers are not looking for you to rush through the task; they care about your communication, how you collaborate, and how you write clean, test-driven code.

Simply Business Software Engineer candidate reports ↗
How fast does the interview process move?

Simply Business is known for running a highly efficient interview process. Many candidates report moving from the initial recruiter screen to a final offer within two weeks, with feedback and next steps often communicated within hours of completing an interview stage.

Simply Business Software Engineer candidate reports ↗
Are there whiteboard or LeetCode-style interviews?

No. Simply Business avoids abstract, academic algorithmic puzzles and whiteboard coding. Their technical evaluations are entirely practical, focusing on real-world scenarios, API design, debugging, and system performance workshops.

Simply Business Software Engineer candidate reports ↗
What is the company's policy on remote and flexible work?

While the company has historically championed flexible and remote-first working arrangements, expectations can vary depending on your specific office location (such as London or Boston) and team requirements. It is best to clarify current hybrid or remote expectations with your recruiter during the initial phone screen.

Simply Business Software Engineer candidate reports ↗
What topics does Simply Business test in interviews?

Simply Business interviews most often cover SQL, Data Interpretation, Problem Solving, Analytical Reasoning, and Requirements Gathering. The exact emphasis depends on the specific role you apply for.

Simply Business Software Engineer candidate reports ↗
Sources & methodology 3 sources ↗

No official company page is cited. Rounds and questions come from candidate reports and PracHub editorial material; each source shows the date it was read.