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EY-Parthenon Software Engineer Interview Guide

EY-Parthenon Software Engineer interview guide: reported rounds, questions and how candidates describe the process.

The 60-second brief

As a Software Engineer at EY-Parthenon, you operate at the unique intersection of software engineering, digital infrastructure, and strategic consulting. This role is pivotal for driving technology-driven transformations, evaluating digital assets, and advising private equity firms and enterprise clients on software company investments. You will contribute to high-stakes strategic initiatives within specialized groups such as the Software Strategy Group and Digital Infrastructure teams, directly influencing product roadmaps, commercial due diligence, and growth platforms. Your day-to-day impact involves analyzing complex software systems, assessing digital portfolios, and engineering scalable solutions that address high-level business challenges.

This guide is scoped to a Software Engineer candidate at EY-Parthenon.

Focus areas

  • Case Interviews
  • Behavioral Interviewing
  • Problem Solving / Analytical Thinking

The EY-Parthenon interview process

EY-Parthenon candidates report 2 rounds over 2-4 weeks. The stages below are what candidates describe, not a published process.

Recruiter Screen

Initial screening by a recruiter to assess candidate fit and qualifications.

What to demonstrate

  • Initial screening by a recruiter to assess candidate fit and qualifications
  • Depth in Case Interviews

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.

Final Round/Superday

Comprehensive interviews with multiple professionals to evaluate advanced case-solving and strategic thinking.

What to demonstrate

  • Comprehensive interviews with multiple professionals to evaluate advanced case-solving and strategic thinking
  • Depth in Case Interviews

How to prepare

  • Answer aloud and timed: Describe a time when you collaborated with cross-functional team members to overcome an ambiguous technical challenge.
  • Answer aloud and timed: Discuss your genuine passion for technology and how you keep your engineering skills sharp.

Where candidates lose points

Embrace the conversational case format

Expect cases that lack a rigid, pre-determined structure; view them as an interactive discussion rather than a test.

Structure your thoughts out loud

When presented with complex graphs or figures, vocalize your hypotheses and analytical steps so the interviewer can follow your reasoning.

Connect technical details to business value

Always tie your engineering insights back to what they mean for a company's market viability, scalability, or investment potential.

Ask insightful questions

Demonstrate genuine interest in the team's work by asking how they measure success and how their advisory projects impact private equity clients.

Refine your technical storytelling

Prepare concise, impactful narratives about your hardest engineering projects, focusing on your personal contributions and problem-solving methodology.

Questions & practice

Analyze a software company in a private equity firm's current portfolio and recommend strategic growth adjustm

Medium · Case Studies & Analytical Problem Solvin

Analyze a software company in a private equity firm's current portfolio and recommend strategic growth adjustments.

Approach

  1. Restate the input: its shape, its size, and what is guaranteed about it.
  2. Name the brute-force solution and its complexity before improving on it.
  3. Choose the data structure from the access pattern, not from familiarity.
  4. State the target complexity and say which constraint rules the naive version out.

Follow-up

  • How does this change if the input no longer fits in memory?
  • What is the worst case, and how likely is it on real data?

Interpret a series of complex, data-heavy graphs and figures to evaluate a target software company's market po

Medium · Case Studies & Analytical Problem Solvin

Interpret a series of complex, data-heavy graphs and figures to evaluate a target software company's market positioning.

Approach

  1. Restate the input: its shape, its size, and what is guaranteed about it.
  2. Name the brute-force solution and its complexity before improving on it.
  3. Choose the data structure from the access pattern, not from familiarity.
  4. State the target complexity and say which constraint rules the naive version out.

Follow-up

  • How does this change if the input no longer fits in memory?
  • What is the worst case, and how likely is it on real data?

Structure a commercial due diligence assessment for a software enterprise looking to scale its digital infrast

Medium · Case Studies & Analytical Problem Solvin

Structure a commercial due diligence assessment for a software enterprise looking to scale its digital infrastructure.

Approach

  1. Restate the input: its shape, its size, and what is guaranteed about it.
  2. Name the brute-force solution and its complexity before improving on it.
  3. Choose the data structure from the access pattern, not from familiarity.
  4. State the target complexity and say which constraint rules the naive version out.

Follow-up

  • How does this change if the input no longer fits in memory?
  • What is the worst case, and how likely is it on real data?

Walk through a prompt engineering case study to evaluate modern software deployment efficiencies.

Medium · Case Studies & Analytical Problem Solvin

Approach

  1. Restate the input: its shape, its size, and what is guaranteed about it.
  2. Name the brute-force solution and its complexity before improving on it.
  3. Choose the data structure from the access pattern, not from familiarity.
  4. State the target complexity and say which constraint rules the naive version out.

Follow-up

  • How does this change if the input no longer fits in memory?
  • What is the worst case, and how likely is it on real data?

Evaluate a target company's technology stack under tight time constraints and present your structural findings

Medium · Case Studies & Analytical Problem Solvin

Evaluate a target company's technology stack under tight time constraints and present your structural findings to senior leadership.

Approach

  1. Restate the input: its shape, its size, and what is guaranteed about it.
  2. Name the brute-force solution and its complexity before improving on it.
  3. Choose the data structure from the access pattern, not from familiarity.
  4. State the target complexity and say which constraint rules the naive version out.

Follow-up

  • How does this change if the input no longer fits in memory?
  • What is the worst case, and how likely is it on real data?

Explain why you want to join this specific group and how you evaluate your professional fit within our culture

Medium · Behavioral & Team Fit

Explain why you want to join this specific group and how you evaluate your professional fit within our culture.

Approach

  1. Name the grain you start from and join outward from it.
  2. Check whether any join is one-to-many before aggregating, or the sums inflate.
  3. Say which index the query would use, and what makes it unusable.
  4. Handle the rows that do not match: that is usually the actual question.

Follow-up

  • How does the query change if that join becomes one-to-many?
  • What happens to this when the table is ten times larger?

Explain why the owner filter ignores the listing index

Medium · composite index · query plans · sort elimination

The only index on resource is (tenant_id, status, updated_at DESC, resource_id DESC). A new endpoint returns one user's resources across all statuses, newest created first: WHERE tenant_id = $1 AND owner_user_id = $2 ORDER BY created_at DESC LIMIT 20. On a tenant with 2M rows it takes 900 ms and EXPLAIN shows a sort above a large scan. Explain precisely why the existing index cannot serve it, give the index that can, and state which of these the new index still will not help: owner_user_id alone across tenants; the same query ordered by updated_at. PostgreSQL 16.

Approach

  1. Separate the two jobs an index does. For filtering, a composite btree is seekable only on a left prefix, so with no predicate on status the scan can at best range over tenant_id and test owner_user_id per row; PostgreSQL 16 has no btree skip scan to jump the unconstrained column.
  2. For ordering, the index is sorted by (status, updated_at) within a tenant and not by created_at, so the LIMIT cannot stop early: every matching row is read and then sorted. That is the 'Sort Method: top-N heapsort' line, and it is why the plan reads 2M rows to answer with 20.
  3. Derive the replacement from the access path — equality, equality, then the ordering column: CREATE INDEX CONCURRENTLY ON resource (tenant_id, owner_user_id, created_at DESC). The scan seeks to the (tenant, owner) range and walks 20 entries in order, so the Sort node disappears along with the row-read.
  4. Treat INCLUDE (title, status) as conditional, not free. An index-only scan still visits the heap for any row whose page is not marked all-visible, so on a table taking 1.2k writes/second the win depends on autovacuum keeping the visibility map current, and the wider index costs more on every insert.

Follow-up

  • 90% of rows are status='active'. Would a partial index WHERE status = 'active' change your answer, and for which of the three queries?
  • A dashboard runs this for 40 owners in one page load. What changes about the design?

Discuss the core components of modern digital infrastructure and how you design systems for high availability.

Medium · Technical & Domain Knowledge

Approach

  1. Fix the scope first: who calls this, how often, and what they do when it fails.
  2. Name the read and write paths separately; they rarely have the same bottleneck.
  3. Choose a partition key and say what query it makes expensive.
  4. State the consistency you need, and where you are willing to be stale.

Follow-up

  • What breaks first when traffic grows ten times?
  • How does this behave when that dependency is down for an hour?

Explain how you approach technical due diligence when assessing a third-party software product.

Medium · Technical & Domain Knowledge

Approach

  1. Clarify what is being asked and what a complete answer contains.
  2. State your assumptions explicitly before working the problem.
  3. Say what you would check first and why it is the highest-information step.
  4. Work from the requirement backwards to the design.

Follow-up

  • What assumption would you test first?
  • How would you know your answer was wrong?

Walk through how you would optimize a legacy software pipeline to meet modern cloud-native standards.

Medium · Technical & Domain Knowledge

Approach

  1. Clarify what is being asked and what a complete answer contains.
  2. State your assumptions explicitly before working the problem.
  3. Say what you would check first and why it is the highest-information step.
  4. Work from the requirement backwards to the design.

Follow-up

  • What assumption would you test first?
  • How would you know your answer was wrong?

Listing latency scales with page size, not with filters

Easy · n+1 · latency · query batching

The tenant listing endpoint reads resource filtered by tenant_id and status, ordered by updated_at DESC, and returns each row plus the owner's display name from app_user and the actor of that resource's latest resource_revision. p99 is 55 ms at 10 rows per page and 1.4 s at 200. Database telemetry shows 401 statements per request, each under 1 ms, and nothing in the slow-query log. Diagnose the cause and give the fix, stating the statement count per request and the p99 you expect afterwards.

Approach

  1. Read the counters before forming a theory. 401 statements for 200 rows is one driver query plus two per row, and sub-millisecond execution with an empty slow-query log rules out a bad plan. The time is round trips, which is why it is invisible in every per-query metric and scales with rows returned rather than with filter selectivity.
  2. Name the two per-row statements from their normalised text: a single-row app_user lookup by user_id, and a resource_revision lookup by resource_id ordered by version DESC LIMIT 1. Confirm by dropping those two response fields and watching the statement count fall to one. That locates the calls in the serialisation layer, not the repository.
  3. Check that the arithmetic accounts for the whole gap. Measure one round trip to the replica in isolation; 400 trips at roughly 3 ms of network plus 0.2 ms of execution is about 1.3 s on top of a 55 ms baseline, which matches. If the multiplication had fallen short, the N+1 would only be part of the story and you would keep looking.
  4. Batch both lookups. Collect owner_user_ids and resource_ids from the driver query, then issue WHERE tenant_id = $1 AND user_id = ANY($2) for the users, and PostgreSQL's SELECT DISTINCT ON (resource_id) ... WHERE resource_id = ANY($2) ORDER BY resource_id, version DESC for the latest revision, which the UNIQUE (resource_id, version) index serves directly. On an engine without DISTINCT ON, use a lateral join or a row_number window. Three statements per request at any page size.

Follow-up

  • The page size is capped at 200 today. What breaks first if it is raised to 2,000, and is it still this bug?
  • How do you stop the next N+1 from reaching production, given that no individual query is slow and the endpoint's tests pass?

Suggested practice checklist

Built from the rounds and topics EY-Parthenon candidates report.

Day 1 — Map the EY-Parthenon loop

  • Write out the reported sequence: Recruiter Screen, Final Round/Superday.
  • 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 2 reported rounds, with the weakest marked.

Day 2 — Work Case Interviews

  • Spend the session on Case Interviews, which EY-Parthenon candidates report being tested on.
  • Write one worked example in Case Interviews and time yourself on it.

Deliverable: One timed worked example in Case Interviews.

Day 3 — Work Behavioral Interviewing

  • Spend the session on Behavioral Interviewing, which EY-Parthenon candidates report being tested on.
  • Write one worked example in Behavioral Interviewing and time yourself on it.

Deliverable: One timed worked example in Behavioral Interviewing.

Day 4 — Work Problem Solving / Analytical Thinking

  • Spend the session on Problem Solving / Analytical Thinking, which EY-Parthenon candidates report being tested on.
  • Write one worked example in Problem Solving / Analytical Thinking and time yourself on it.

Deliverable: One timed worked example in Problem Solving / Analytical Thinking.

Day 5 — Answer out loud: Behavioral & Team Fit

  • Answer aloud, timed: Assess how your past professional background aligns with the specific team and responsibilities at EY-Parthenon.
  • Answer aloud, timed: Walk through your hardest technical project and explain how you successfully solved the core problems involved.

Deliverable: Spoken answers to 2 reported Behavioral & Team Fit question(s), under time.

Day 6 — Answer out loud: Case Studies & Analytical Problem Solving

  • Answer aloud, timed: Analyze a software company in a private equity firm's current portfolio and recommend strategic growth adjustments.
  • Answer aloud, timed: Interpret a series of complex, data-heavy graphs and figures to evaluate a target software company's market positioning.

Deliverable: Spoken answers to 2 reported Case Studies & Analytical Problem Solving question(s), under time.

Day 7 — Answer out loud: Technical & Domain Knowledge

  • Answer aloud, timed: Discuss the core components of modern digital infrastructure and how you design systems for high availability.
  • Answer aloud, timed: Explain how you approach technical due diligence when assessing a third-party software product.

Deliverable: Spoken answers to 2 reported Technical & Domain Knowledge question(s), under time.

Behavioural preparation

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

Assess how your past professional background aligns with the specific team and responsibilities at EY-Partheno

Medium · Behavioral & Team Fit

Assess how your past professional background aligns with the specific team and responsibilities at EY-Parthenon.

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?

Walk through your hardest technical project and explain how you successfully solved the core problems involved

Medium · Behavioral & Team Fit

Walk through your hardest technical project and explain how you successfully solved the core problems involved.

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 collaborated with cross-functional team members to overcome an ambiguous technical ch

Medium · Behavioral & Team Fit

Describe a time when you collaborated with cross-functional team members to overcome an ambiguous technical challenge.

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?

Discuss your genuine passion for technology and how you keep your engineering skills sharp.

Medium · Behavioral & Team Fit

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 your experience with data-heavy engineering challenges and how you ensure system scalability.

Medium · Technical & Domain Knowledge

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?