A Software Engineer at the University of Pennsylvania (Penn) occupies a unique and vital role at the intersection of high-level academia and enterprise-grade technology. Unlike traditional tech firms, Penn utilizes its engineering talent to solve problems that range from managing massive institutional data systems to building bespoke software that powers groundbreaking medical and scientific research. Whether you are assigned to a central administrative team like Information Systems and Computing (ISC) or a specific school such as Penn Medicine or Wharton, your work directly enables the university’s mission of education and research. The impact of this position is profound. You might develop applications that streamline the student experience for tens of thousands of users or build data pipelines that allow Principal Investigators (PIs) to process complex genomic data. This role requires a high degree of stewardship and, as you will often be the bridge between technical possibilities and the needs of world-renowned researchers and administrators. intellectual curiosity Working at Penn offers the stability of a world-class institution combined with the challenge of a highly decentralized and complex technical environment. Candidates should expect to work on diverse projects that require both a deep understanding of software architecture and a collaborative spirit capable of navigating a mission-driven organization.
Application Review
reportedInitial review of submitted applications to assess qualifications and fit for the role.
What to demonstrate
- Initial review of submitted applications to assess qualifications and fit for the role
- Depth in Technical Interviewing
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.
On-Demand Video Interview
reportedCandidates record answers to specific questions for review by the hiring committee.
What to demonstrate
- Candidates record answers to specific questions for review by the hiring committee
- Depth in Technical Interviewing
How to prepare
- Answer aloud and timed: Describe the difference between an inner join and an outer join in SQL.
- Answer aloud and timed: Explain how a RESTful API works and what the common HTTP methods represent.
Technical Phone Screen
reportedA technical interview conducted via phone or video call with a lead engineer or manager.
What to demonstrate
- A technical interview conducted via phone or video call with a lead engineer or manager
- Depth in Technical Interviewing
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.
Onsite Interview
reportedA comprehensive interview where candidates meet the broader team, including senior staff and stakeholders.
What to demonstrate
- A comprehensive interview where candidates meet the broader team
- Including senior staff and stakeholders
How to prepare
- Answer aloud and timed: Tell us about a time you had a disagreement with a teammate. How did you resolve it?
- Answer aloud and timed: How do you stay current with new technologies and industry trends?
PracHub editorial advice for the preparation topics above.
Research the School or Lab
Penn is decentralized. A role in the Perelman School of Medicine will have a very different culture and tech stack than a role in ISC. Tailor your preparation to the specific department you are interviewing with.
Highlight "Service
Mentioning your desire to contribute to the university’s broader mission of research and education can be a strong differentiator.
Prepare for Non-Technical Interviewers
You will likely meet a Director or a PI who cares more about what the software does for their mission than how it is implemented. Be ready to discuss the business or research value of your work.
Do not neglect your behavioral preparation
At Penn, being a "culture fit" and a good communicator is often just as important as your technical skill set.
Choose a category, try a prompt, then open its approach, worked solution or follow-up when you need it.
Implement a function to determine if a string is a palindrome.
Implement a function to determine if a string is a palindrome.
Approach
- Restate the input: its shape, its size, and what is guaranteed about it.
- Name the brute-force solution and its complexity before improving on it.
- Choose the data structure from the access pattern, not from familiarity.
- 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?
How would you find the shortest path between two nodes in a graph?
How would you find the shortest path between two nodes in a graph?
Approach
- Restate the input: its shape, its size, and what is guaranteed about it.
- Name the brute-force solution and its complexity before improving on it.
- Choose the data structure from the access pattern, not from familiarity.
- 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?
Collapse a redelivered event batch into per-aggregate high-water marks
You drain a batch of up to 5,000,000 events, each (aggregate_id BIGINT, aggregate_version INT, event_type, payload). The log guarantees order within one aggregate only; the batch merges 64 partitions, and a relay failover has redelivered a range, so an older version for an aggregate can appear after a newer one. Given a map of last_applied_version per aggregate, produce the events worth applying, at most one per (aggregate_id, version), plus the count discarded. Target O(n) time. State the memory for 2,000,000 distinct aggregates and what you do when it does not fit.
Approach
- One pass, one hash map from aggregate_id to the highest version kept, and a discard counter. An event whose version is at or below last_applied_version for its aggregate is dropped without further work, which is the whole reason the event carries its version rather than a delta. O(n) expected time, O(d) space in distinct aggregates.
- Keep the maximum, never the last occurrence. The redelivered range means the final appearance of an aggregate in the batch can be an older version than one seen earlier in the same batch, so last-wins applies stale state over newer state and the projection regresses with no error anywhere.
- Cost the memory instead of calling it large: an 8-byte key plus a 4-byte version is 12 bytes of payload, and an open-addressed table held at a 0.7 load factor costs roughly 17 bytes per entry before per-slot metadata, so 2,000,000 aggregates is tens of megabytes in a native layout and several times that in a runtime that boxes both key and value.
- If the distinct set exceeds memory, partition on hash(aggregate_id) mod P and reduce each partition independently. Every event for one aggregate hashes to the same partition, so the per-partition result is exact and the merge is concatenation rather than a second reduction.
Follow-up
- The payload is a patch rather than a snapshot, so applying only the highest version loses the intermediate changes. What changes in your reduction?
- How do you detect that version 7 arrived while version 6 was never delivered, and what should the consumer do about the gap?
Describe the difference between an inner join and an outer join in SQL.
Describe the difference between an inner join and an outer join in SQL.
Approach
- Name the grain you start from and join outward from it.
- Check whether any join is one-to-many before aggregating, or the sums inflate.
- Say which index the query would use, and what makes it unusable.
- 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
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
- 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.
- 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.
- 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.
- 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?
Explain how a RESTful API works and what the common HTTP methods represent.
Explain how a RESTful API works and what the common HTTP methods represent.
Approach
- Say who the caller is and what they do when the call fails halfway.
- Define the identity of a request so a retry cannot double-apply it.
- Separate accepted, pending, failed and confirmed; they are different facts.
- Design the error taxonomy before the success shape; callers branch on it.
Follow-up
- What happens if the caller retries after a timeout?
- How does a client discover it is on an old version of this contract?
Write a script to parse a large log file and extract specific error patterns.
Write a script to parse a large log file and extract specific error patterns.
Approach
- Clarify what is being asked and what a complete answer contains.
- State your assumptions explicitly before working the problem.
- Say what you would check first and why it is the highest-information step.
- Work from the requirement backwards to the design.
Follow-up
- What assumption would you test first?
- How would you know your answer was wrong?
How do you prioritize tasks when you are working on multiple projects with tight deadlines?
How do you prioritize tasks when you are working on multiple projects with tight deadlines?
Approach
- Clarify what is being asked and what a complete answer contains.
- State your assumptions explicitly before working the problem.
- Say what you would check first and why it is the highest-information step.
- 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 us through your typical workflow for debugging a production issue.
Walk us through your typical workflow for debugging a production issue.
Approach
- Establish what changed and when, before forming any theory.
- Pick a bisection that eliminates candidates whichever way it turns out.
- Check the instrumentation before believing the symptom.
- Separate the trigger from the cause; the deploy is rarely the bug.
Follow-up
- What would you look at first, and what would it rule out?
- How would you tell a cause from a coincidence here?
Built from the rounds and topics University of Pennsylvania candidates report.
Prepare, practise & reflect
One practical outcome each day. Spend longer where you need it.
0 / 7 done01Map the University of Pennsylvania loop
- Write out the reported sequence: Application Review, On-Demand Video Interview, Technical Phone Screen, Onsite Interview.
- 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 Technical Interviewing
- Spend the session on Technical Interviewing, which University of Pennsylvania candidates report being tested on.
- Write one worked example in Technical Interviewing and time yourself on it.
Deliverable: One timed worked example in Technical Interviewing.
03Work Problem Solving
- Spend the session on Problem Solving, which University of Pennsylvania candidates report being tested on.
- Write one worked example in Problem Solving and time yourself on it.
Deliverable: One timed worked example in Problem Solving.
04Work Algorithms
- Spend the session on Algorithms, which University of Pennsylvania candidates report being tested on.
- Write one worked example in Algorithms and time yourself on it.
Deliverable: One timed worked example in Algorithms.
05Answer out loud: Technical & CS Fundamentals
- Answer aloud, timed: Implement a function to determine if a string is a palindrome.
- Answer aloud, timed: How would you find the shortest path between two nodes in a graph?
Deliverable: Spoken answers to 2 reported Technical & CS Fundamentals question(s), under time.
06Answer out loud: Behavioral & Situational
- Answer aloud, timed: Describe a difficult technical challenge you faced and how you overcame it.
- Answer aloud, timed: Tell us about a time you had a disagreement with a teammate. How did you resolve it?
Deliverable: Spoken answers to 2 reported Behavioral & Situational question(s), under time.
07Answer out loud: System & Process
- Answer aloud, timed: How do you approach testing your code? Describe your experience with Unit Testing.
- Answer aloud, timed: Walk us through your typical workflow for debugging a production issue.
Deliverable: Spoken answers to 2 reported System & Process 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 a difficult technical challenge you faced and how you overcame it.
Describe a difficult technical challenge you faced and how you overcame it.
Approach
- Pick a story where you made the decision, not one where you watched it.
- State the situation in two sentences and spend the rest on the reasoning.
- Give the blast radius: what could have broken, and what you measured.
- 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 us about a time you had a disagreement with a teammate. How did you resolve it?
Tell us about a time you had a disagreement with a teammate. How did you resolve it?
Approach
- Pick a story where you made the decision, not one where you watched it.
- State the situation in two sentences and spend the rest on the reasoning.
- Give the blast radius: what could have broken, and what you measured.
- 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?
How do you stay current with new technologies and industry trends?
How do you stay current with new technologies and industry trends?
Approach
- Pick a story where you made the decision, not one where you watched it.
- State the situation in two sentences and spend the rest on the reasoning.
- Give the blast radius: what could have broken, and what you measured.
- 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 time you had to work with an ambiguous set of requirements.
Give an example of a time you had to work with an ambiguous set of requirements.
Approach
- Pick a story where you made the decision, not one where you watched it.
- State the situation in two sentences and spend the rest on the reasoning.
- Give the blast radius: what could have broken, and what you measured.
- 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?
Why do you want to work for the University of Pennsylvania specifically?
Why do you want to work for the University of Pennsylvania specifically?
Approach
- Pick a story where you made the decision, not one where you watched it.
- State the situation in two sentences and spend the rest on the reasoning.
- Give the blast radius: what could have broken, and what you measured.
- 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?
How do you approach testing your code? Describe your experience with Unit Testing.
How do you approach testing your code? Describe your experience with Unit Testing.
Approach
- Pick a story where you made the decision, not one where you watched it.
- State the situation in two sentences and spend the rest on the reasoning.
- Give the blast radius: what could have broken, and what you measured.
- 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 a difficult technical challenge you faced and how you overcame it.
- 02
Tell us about a time you had a disagreement with a teammate. How did you resolve it?
- 03
How do you stay current with new technologies and industry trends?
- 04
Give an example of a time you had to work with an ambiguous set of requirements.
How difficult are the technical interviews at Penn?
The difficulty is generally rated as average to difficult. While you may not face the "leetscode-hard" puzzles typical of some Big Tech firms, you will be expected to have a very strong grasp of CS 101 fundamentals and be able to apply them to practical, real-world scenarios.
University of Pennsylvania Software Engineer candidate reports ↗What is the work-life balance like for engineers?
Penn is known for offering an excellent work-life balance compared to the private sector. The university provides generous benefits, ample time off, and a culture that generally respects personal time, though certain "crunch periods" may occur around major academic cycles or project launches.
University of Pennsylvania Software Engineer candidate reports ↗How long does the hiring process take?
The process can be slower than at a startup. From the initial application to a final offer, it can take anywhere from 4 to 8 weeks. This is due to the committee-based review process and the need for various levels of administrative approval.
University of Pennsylvania Software Engineer candidate reports ↗Is there a specific "Penn style" of coding?
There is a strong emphasis on maintainability and documentation. Because systems at a university often last for many years and may be handed off between different developers or students, writing code that is easy for others to read and support is highly valued.
University of Pennsylvania Software Engineer candidate reports ↗What topics does University of Pennsylvania test in interviews?
University of Pennsylvania interviews most often cover Stakeholder Management, Stakeholder Communication, Requirements Gathering, Data Interpretation, and SAS programming. The exact emphasis depends on the specific role you apply for.
University of Pennsylvania 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.
- 01University of Pennsylvania Software Engineer candidate reports ↗
Company-reported rounds, questions and FAQ.
Candidate reports · Accessed 2026-09-22 - 02PracHub Software Engineer practice ↗
PracHub practice material, not company-reported.
PracHub page · Accessed 2026-09-22 - 03PracHub preparation framework ↗
PracHub preparation guidance.
PracHub page · Accessed 2026-09-22
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