As a Software Engineer at Oak Street Health, you play a pivotal role in advancing the company's mission to provide high-quality healthcare to underserved communities. Your work contributes directly to the development and enhancement of innovative software solutions that improve patient care and operational efficiency. This position is integral to building systems that support the delivery of essential healthcare services, making it both a critical and fulfilling role. In this position, you will engage with various teams to design, implement, and maintain applications that are crucial for patient management, data analytics, and operational workflows. The complexity of the healthcare landscape presents unique challenges, offering an exciting opportunity to leverage technology in impactful ways. Whether you are working on improving existing systems or developing new applications, your contributions will significantly influence the user experience and overall effectiveness of healthcare delivery at Oak Street Health.
Phone Interview
reportedInitial call with a hiring manager to discuss your background and experiences.
What to demonstrate
- Initial call with a hiring manager to discuss your background and experiences
- Depth in .NET (C#)
How to prepare
- Answer aloud and timed: Explain the behavior of a given piece of.NET code.
- Answer aloud and timed: How would you share data between microservices?
Technical Interview
reportedIn-depth technical interview, possibly in a panel format, to evaluate your skills.
What to demonstrate
- In-depth technical interview, possibly in a panel format, to evaluate your skills
- Depth in .NET (C#)
How to prepare
- Answer aloud and timed: What best practices do you follow in API development?
- Answer aloud and timed: Can you describe a challenging technical problem you solved in a previous project?
Behavioral Assessment
reportedAssessment focusing on cultural fit and collaboration within the team.
What to demonstrate
- Assessment focusing on cultural fit and collaboration within the team
- Depth in .NET (C#)
How to prepare
- Prepare three examples from your own work, each with a decision you made and an outcome you can quantify.
- Re-read the description of the behavioral assessment above and write down what you would ask to confirm before it.
PracHub editorial advice for the preparation topics above.
Understand the Mission
Familiarize yourself with Oak Street Health’s mission and how technology supports it. This knowledge will help you articulate your fit for the role.
Prepare Scenario-Based Examples
Have examples ready that demonstrate your problem-solving skills and how you’ve navigated challenges in past projects.
Practice Clear Communication
Be prepared to explain your technical decisions in a way that non-technical stakeholders can understand.
Ask Insightful Questions
Prepare thoughtful questions that show your interest in the company and the role, particularly around team dynamics and project priorities.
Choose a category, try a prompt, then open its approach, worked solution or follow-up when you need it.
Describe how you would approach a data manipulation task without using LeetCode-style algorithms.
Describe how you would approach a data manipulation task without using LeetCode-style algorithms.
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?
Solve a coding challenge related to data structures or algorithms.
Solve a coding challenge related to data structures or algorithms.
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?
Archive a resource graph without breaking live references or recursing
Resources reference other resources within a tenant; for the largest tenant the reference table holds up to 2,000,000 nodes and 8,000,000 edges. Archiving a resource must archive everything reachable from it that nothing outside the set still references, refuse when a live external referrer exists, and terminate when references form cycles, which they legitimately do. Produce the archive order and the refusal list, targeting O(V+E). Say what stops the traversal crossing a tenant boundary, and why recursion is the wrong control structure at this size.
Approach
- Load the subgraph with the tenant predicate on both endpoints of the edge, not only on the side you started from. Scoping the left table alone is the classic cross-tenant leak: one mis-entered edge then pulls another tenant's resources into the traversal and, worse, into the archive.
- Traverse iteratively with an explicit stack. A 2,000,000-node graph can hold a chain deep enough to exhaust a native stack in the low tens of thousands of frames, and that failure is a process crash rather than an error you can return.
- Treat cycles as data rather than corruption: compute strongly connected components with Tarjan in O(V+E) using its own explicit stack, then condense. The condensation is a DAG, so a topological order over it gives the archive order, and every member of a component archives in one transaction because no order within a cycle is valid.
- Decide refusals with reverse edges. A candidate is archivable only if every in-edge originates inside the candidate set, so build the transpose or count in-degrees restricted to the visited set, and emit each blocked resource with the id of the external referrer, which is the only part of the answer an operator can act on.
Follow-up
- The graph is read in one query and the archive writes a minute later. What can change in between, and how do you make the write safe?
- The candidate set is 400,000 resources. Is that one transaction, and if not, what does a half-finished archive look like to a reader?
Provide a solution to a basic SQL query problem.
Provide a solution to a basic SQL query problem.
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?
Stop tag and share joins from fanning out a page
resource_tag is (resource_id, tag_id) with PK (resource_id, tag_id); resource_share is (resource_id, shared_with_user_id, permission). The tagged-and-shared listing inner-joins resource to both, filters tenant_id, tag_id = ANY($2) and shared_with_user_id = $3, orders by updated_at DESC and takes 50. Pages come back with fewer than 50 distinct resources and the total in the header is far too high. Explain the row multiplication, rewrite both the page query and the count query so each is correct, and name the index each one needs. PostgreSQL 16.
Approach
- Do the arithmetic against the predicates that are actually there. An inner join emits one row per matching child row, and both joins are filtered: tag_id = ANY($2) admits only the requested tags, shared_with_user_id = $3 admits one user's share rows. So a resource holding three of the requested tags and shared with $3 once yields three rows, not one — the multiplier is its count of matching tags times its share rows for that single user, and that second factor is 1 unless the table admits duplicate (resource_id, shared_with_user_id) pairs. LIMIT 50 then limits rows rather than resources, and COUNT(*) counts pairs — the header is the product, not the population.
- Reject DISTINCT as the fix. It deduplicates after the product has been built, so the planner must materialise and sort the fanned-out set before the LIMIT can apply, and it leaves any SUM or AVG in the same select list wrong.
- Rewrite both filters as semi-joins, keeping resource as the only row source: AND EXISTS (SELECT 1 FROM resource_tag rt WHERE rt.resource_id = r.resource_id AND rt.tag_id = ANY($2)) and the same shape against resource_share. A semi-join stops at the first match per resource and preserves the driving index order, so ORDER BY updated_at DESC, resource_id DESC LIMIT 50 still stops after 50 rows.
- Count with the same predicates and no join at all: SELECT count(*) FROM resource r WHERE r.tenant_id = $1 AND r.status = 'active' AND EXISTS (...) AND EXISTS (...). Nothing multiplies a resource, so the number is the population.
Follow-up
- The filter changes from 'any of these tags' to 'all of these tags'. Rewrite it and state what it costs relative to the ANY form.
- A resource can be shared with the same user twice under different permissions. Does your count change, and should it?
Explain the behavior of a given piece of.NET code.
Explain the behavior of a given piece of.NET code.
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 would you share data between microservices?
How would you share data between microservices?
Approach
- Fix the scope first: who calls this, how often, and what they do when it fails.
- Name the read and write paths separately; they rarely have the same bottleneck.
- Choose a partition key and say what query it makes expensive.
- 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?
What best practices do you follow in API development?
What best practices do you follow in API development?
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?
Can you describe a challenging technical problem you solved in a previous project?
Can you describe a challenging technical problem you solved in a previous project?
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 manage state in Vue.js (or your preferred framework)?
How do you manage state in Vue.js (or your preferred framework)?
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?
If faced with a scaling issue in a distributed system, what strategies would you employ?
If faced with a scaling issue in a distributed system, what strategies would you employ?
Approach
- Fix the scope first: who calls this, how often, and what they do when it fails.
- Name the read and write paths separately; they rarely have the same bottleneck.
- Choose a partition key and say what query it makes expensive.
- 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?
Design a simple microservices architecture for a healthcare application.
Design a simple microservices architecture for a healthcare application.
Approach
- Fix the scope first: who calls this, how often, and what they do when it fails.
- Name the read and write paths separately; they rarely have the same bottleneck.
- Choose a partition key and say what query it makes expensive.
- 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?
How would you ensure data consistency across distributed systems?
How would you ensure data consistency across distributed systems?
Approach
- Fix the scope first: who calls this, how often, and what they do when it fails.
- Name the read and write paths separately; they rarely have the same bottleneck.
- Choose a partition key and say what query it makes expensive.
- 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?
How would you troubleshoot a performance issue in a web application?
How would you troubleshoot a performance issue in a web application?
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 Oak Street Health candidates report.
Prepare, practise & reflect
One practical outcome each day. Spend longer where you need it.
0 / 7 done01Map the Oak Street Health loop
- Write out the reported sequence: Phone Interview, Technical Interview, Behavioral Assessment.
- 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 3 reported rounds, with the weakest marked.
02Work .NET (C#)
- Spend the session on .NET (C#), which Oak Street Health candidates report being tested on.
- Write one worked example in .NET (C#) and time yourself on it.
Deliverable: One timed worked example in .NET (C#).
03Work REST APIs
- Spend the session on REST APIs, which Oak Street Health candidates report being tested on.
- Write one worked example in REST APIs and time yourself on it.
Deliverable: One timed worked example in REST APIs.
04Work SQL
- Spend the session on SQL, which Oak Street Health candidates report being tested on.
- Write one worked example in SQL and time yourself on it.
Deliverable: One timed worked example in SQL.
05Answer out loud: Technical / Domain Questions
- Answer aloud, timed: Explain the behavior of a given piece of.NET code.
- Answer aloud, timed: How would you share data between microservices?
Deliverable: Spoken answers to 2 reported Technical / Domain Questions question(s), under time.
06Answer out loud: Problem-Solving / Case Studies
- Answer aloud, timed: Describe how you would approach a data manipulation task without using LeetCode-style algorithms.
- Answer aloud, timed: If faced with a scaling issue in a distributed system, what strategies would you employ?
Deliverable: Spoken answers to 2 reported Problem-Solving / Case Studies question(s), under time.
07Answer out loud: Behavioral / Leadership Questions
- Answer aloud, timed: Describe a time you disagreed with a team member and how you handled the situation.
- Answer aloud, timed: What motivates you to perform well in your role?
Deliverable: Spoken answers to 2 reported Behavioral / Leadership Questions 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 time you disagreed with a team member and how you handled the situation.
Describe a time you disagreed with a team member and how you handled the situation.
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 motivates you to perform well in your role?
What motivates you to perform well in your role?
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 prioritize tasks when working on multiple projects?
How do you prioritize tasks when working on multiple projects?
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 time you disagreed with a team member and how you handled the situation.
- 02
What motivates you to perform well in your role?
- 03
How do you prioritize tasks when working on multiple projects?
What is the typical interview difficulty level?
Most candidates find the interviews at Oak Street Health to be moderately challenging. Adequate preparation can help you feel confident and ready to showcase your skills.
Oak Street Health Software Engineer candidate reports ↗What differentiates successful candidates?
Successful candidates often demonstrate not only technical proficiency but also a clear alignment with the company's mission and values. Strong problem-solving abilities and effective communication skills are key.
Oak Street Health Software Engineer candidate reports ↗What is the culture like at Oak Street Health?
The culture emphasizes collaboration, empathy, and innovation. Employees are encouraged to contribute ideas and work together to enhance patient care.
Oak Street Health Software Engineer candidate reports ↗How long does the interview process typically take?
The timeline can vary, but candidates generally expect the process to take several weeks from the initial application to the final offer.
Oak Street Health Software Engineer candidate reports ↗Are there remote or hybrid work options?
Depending on the role and team, there may be flexibility for remote or hybrid work arrangements, especially in light of recent trends in the workplace.
Oak Street Health Software Engineer candidate reports ↗What topics does Oak Street Health test in interviews?
Oak Street Health interviews most often cover Stakeholder Management, Automation Testing, Cross-Functional Collaboration, Data Modeling, and Business Analysis (BA). The exact emphasis depends on the specific role you apply for.
Oak Street Health 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.
- 01Oak Street Health 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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