As a Software Engineer at OSF HealthCare, you are stepping into a role where your technical expertise directly supports patient care, clinical workflows, and enterprise operations. OSF HealthCare relies on robust, secure, and scalable software to manage health records, patient portals, and internal administrative tools. Your work ensures that medical professionals have the reliable systems they need to make life-saving decisions and that patients have seamless access to their health information. This position offers a unique blend of technical challenge and mission-driven impact. You will be building and maintaining critical applications, often working within a complex ecosystem of healthcare data integrations. Because the healthcare industry demands high standards for security and reliability, your role requires a careful balance of innovative problem-solving and rigorous adherence to best practices. Expect to work in a highly collaborative environment. Our engineering teams operate at the intersection of technology and healthcare delivery, meaning you will frequently interact with cross-functional stakeholders, including clinical staff, product managers, and other engineering units. If you are passionate about leveraging your coding skills to make a tangible difference in people's lives, this role provides the perfect platform to do so.
HR Screening
reportedInitial screening via email or phone call to align background, salary expectations, and basic qualifications.
What to demonstrate
- Initial screening via email or phone call to align background, salary expectations, and basic qualifications
- Depth in C#
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.
Panel Interview
reportedInterview with multiple managers and staff members, focusing on technical skills, past experience, and cultural fit.
What to demonstrate
- Interview with multiple managers and staff members
- Focusing on technical skills, past experience, and cultural fit
How to prepare
- Answer aloud and timed: Can you explain dependency injection and how you have used it in ASP.NET Core?
- Answer aloud and timed: Walk me through how you would optimize a slow-loading web page backed by a SQL database.
PracHub editorial advice for the preparation topics above.
Prepare for Small Talk
Unlike some rigid tech interviews, OSF HealthCare panels often include casual, non-work-related topics. Be ready to discuss your hobbies, interests, and background naturally. Building personal rapport with the managers is just as important as nailing the technical questions.
Highlight Your Growth Mindset
Our teams value continuous education. Be sure to express enthusiasm for our internal training processes and any certifications you might have the opportunity to earn.
Know Your Resume Inside and Out
Interviewers will ask you to recap your previous experience in detail. Be prepared to speak confidently about every technology, project, and duty listed on your resume. If it is on the page, it is fair game for discussion.
Choose a category, try a prompt, then open its approach, worked solution or follow-up when you need it.
Diff a projection against the primary without per-row point reads
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
- 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.
- 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.
- 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.
- 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?
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?
Identify the heaviest tenants in a five-minute window under memory pressure
The edge service handles about 3,000 requests per second across roughly 50,000 tenants, peaking near 9,000. Expose the 50 heaviest tenants by request count over the trailing five minutes so limits can be tightened before one tenant's backfill starves the fleet. You may not retain five minutes of raw records. Give the exact solution and its memory, then the bounded-memory approximation with its error stated as a formula, and say which you would ship and at what tenant cardinality that choice changes.
Approach
- Do the exact version first, because it is affordable at this cardinality: a ring of 300 one-second counters per tenant, advanced lazily, is 1,200 bytes of counters per tenant and roughly 60 to 90 MB for 50,000 tenants with overhead. Carry a running total and subtract the bucket you overwrite so a window read is O(1) rather than 300 adds.
- Extract the top 50 with a size-k min-heap over the tenant sums: O(d log k) for d tenants, against O(d log d) to sort them all. Maintaining the heap continuously instead of on query requires a tenant-to-heap-index map, because incrementing a count already inside the heap means sifting from a known position, and without that map you rebuild the heap on every request.
- State the approximation precisely rather than gesturing at sketches. Misra-Gries with m counters retains every item whose true count exceeds N/(m+1), and each retained count underestimates the truth by at most N/(m+1). With m = 1,000 and N = 900,000 requests in the window the error is roughly 900 requests, which is fine for spotting a tenant sending 50,000 and useless for ranking two tenants 200 apart.
- Say what breaks when the window slides: Misra-Gries and Space-Saving are insert-only and cannot be decremented as records age out. The workable construction is one summary per sub-window, say ten seconds, with 30 summaries merged at query time, and the merged error is the sum of the per-summary errors, so the bound degrades linearly in the number of sub-windows.
Follow-up
- The heaviest tenant is heavy because of one export job rather than user traffic. Should the limiter treat those as the same tenant?
- Two tenants sit tied at the boundary of the top 50. Does your answer flap, and does the flapping matter?
Walk me through how you would optimize a slow-loading web page backed by a SQL database.
Walk me through how you would optimize a slow-loading web page backed by a SQL database.
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?
What are the main differences between.NET Framework and.NET Core?
What are the main differences between.NET Framework and.NET Core?
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?
Can you explain dependency injection and how you have used it in ASP.NET Core?
Can you explain dependency injection and how you have used it in ASP.NET Core?
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 ensure your code is secure, especially when handling sensitive user data?
How do you ensure your code is secure, especially when handling sensitive user data?
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 me through your resume, highlighting the roles most relevant to this position.
Walk me through your resume, highlighting the roles most relevant to this position.
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?
Describe your day-to-day duties in your most recent Software Engineer role.
Describe your day-to-day duties in your most recent Software Engineer role.
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?
What is a technical achievement you are particularly proud of, and what was your specific contribution?
What is a technical achievement you are particularly proud of, and what was your specific contribution?
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?
Have you ever earned any technical certifications, or what is your approach to continuous training?
Have you ever earned any technical certifications, or what is your approach to continuous training?
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?
Listing latency scales with page size, not with filters
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
- 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.
- 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.
- 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.
- 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?
Built from the rounds and topics OSF HealthCare candidates report.
Prepare, practise & reflect
One practical outcome each day. Spend longer where you need it.
0 / 7 done01Map the OSF HealthCare loop
- Write out the reported sequence: HR Screening, Panel 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 2 reported rounds, with the weakest marked.
02Work C#
- Spend the session on C#, which OSF HealthCare candidates report being tested on.
- Write one worked example in C# and time yourself on it.
Deliverable: One timed worked example in C#.
03Work .NET (General)
- Spend the session on .NET (General), which OSF HealthCare candidates report being tested on.
- Write one worked example in .NET (General) and time yourself on it.
Deliverable: One timed worked example in .NET (General).
04Work Technical Interviewing
- Spend the session on Technical Interviewing, which OSF HealthCare 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.
05Answer out loud: Technical and Technology Stack Questions
- Answer aloud, timed: What are the main differences between.NET Framework and.NET Core?
- Answer aloud, timed: How do you handle exception management and logging in a C# application?
Deliverable: Spoken answers to 2 reported Technical and Technology Stack Questions question(s), under time.
06Answer out loud: Experience and Resume Deep-Dive
- Answer aloud, timed: Walk me through your resume, highlighting the roles most relevant to this position.
- Answer aloud, timed: Describe your day-to-day duties in your most recent Software Engineer role.
Deliverable: Spoken answers to 2 reported Experience and Resume Deep-Dive question(s), under time.
07Answer out loud: Behavioral and Culture Fit
- Answer aloud, timed: Tell me about a time you disagreed with a team member about a technical approach. How did you resolve it?
- Answer aloud, timed: Why do you want to work for OSF HealthCare?
Deliverable: Spoken answers to 2 reported Behavioral and Culture Fit 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.
How do you handle exception management and logging in a C# application?
How do you handle exception management and logging in a C# application?
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 me about a time you had to learn a new technology stack on the fly.
Tell me about a time you had to learn a new technology stack on the fly.
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 me about a time you disagreed with a team member about a technical approach. How did you resolve it?
Tell me about a time you disagreed with a team member about a technical approach. 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?
Why do you want to work for OSF HealthCare?
Why do you want to work for OSF HealthCare?
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 handle situations where project requirements are ambiguous or constantly changing?
How do you handle situations where project requirements are ambiguous or constantly changing?
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?
What are some of your hobbies or interests outside of software development?
What are some of your hobbies or interests outside of software development?
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?
Describe a time you had to collaborate with a team outside of engineering to get a project done.
Describe a time you had to collaborate with a team outside of engineering to get a project done.
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
How do you handle exception management and logging in a C# application?
- 02
Tell me about a time you had to learn a new technology stack on the fly.
- 03
Tell me about a time you disagreed with a team member about a technical approach. How did you resolve it?
- 04
Why do you want to work for OSF HealthCare?
How difficult is the interview process, and how much should I prepare?
The difficulty is generally considered average. While the technical questions on C# and.NET require solid foundational knowledge, the interview avoids overly esoteric brain-teasers. Focus your preparation on articulating your past experience clearly and brushing up on core Microsoft stack concepts.
OSF HealthCare Software Engineer candidate reports ↗Who will I be interviewing with during the panel stage?
You will typically meet with multiple managers and staff members. Interestingly, this panel often includes managers from other engineering teams, not just the one you are applying for. This is designed to assess your broader fit within the OSF HealthCare engineering culture.
OSF HealthCare Software Engineer candidate reports ↗What differentiates a successful candidate from the rest?
Successful candidates strike a balance between technical competence and approachability. Because the interviews feature a decent amount of non-work-based, casual conversation, candidates who are personable, communicative, and show a genuine willingness to learn and train generally stand out.
OSF HealthCare Software Engineer candidate reports ↗Will the interview be in-person or virtual?
Historically, many of our panel interviews, especially for roles based near our Peoria, IL headquarters, have been conducted in person. However, hybrid and virtual options are often utilized depending on the specific team and your location. Always confirm the format with your HR coordinator.
OSF HealthCare Software Engineer candidate reports ↗Do I need prior healthcare industry experience to be hired?
No, prior healthcare experience is not strictly required. While familiarity with healthcare data systems is a nice bonus, we are primarily looking for strong software engineering fundamentals and a passion for our mission. We provide training on the specific healthcare domain knowledge you will need.
OSF HealthCare Software Engineer candidate reports ↗What topics does OSF HealthCare test in interviews?
OSF HealthCare interviews most often cover SQL, Python, Problem Solving, Business Analysis, and C#. The exact emphasis depends on the specific role you apply for.
OSF HealthCare 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.
- 01OSF HealthCare 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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