A Software Engineer at Hazel Health plays a critical role in transforming how pediatric healthcare is delivered. By building and scaling the industry's leading school-based telehealth platform, engineering teams directly impact millions of students who need rapid, reliable access to physical and mental health services. The technology you develop ensures that school nurses, parents, and healthcare providers can seamlessly collaborate to deliver care when and where it is needed most. The engineering challenges at Hazel Health are both complex and highly rewarding. You will work on real-time video communications, secure health records management, clinical scheduling systems, and data pipelines that must remain robust under high demand. Because this platform serves as a lifeline for vulnerable student populations, security, accessibility, and high availability are not just technical goals—they are ethical imperatives. Joining this team means committing to a mission-driven environment where your technical decisions have immediate, real-world consequences. As a Software Engineer, you will collaborate closely with product managers, clinical operations, and design teams to build intuitive, HIPAA-compliant software. It is a unique opportunity to apply modern software engineering practices to solve some of the most pressing systemic challenges in healthcare accessibility today.
Application Review
reportedInitial review of your application and resume to assess qualifications.
What to demonstrate
- Initial review of your application and resume to assess qualifications
- Depth in Software Engineering (General)
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.
Behavioral Screen
reportedCasual conversation focusing on your background and career trajectory.
What to demonstrate
- Casual conversation focusing on your background and career trajectory
- Depth in Software Engineering (General)
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 screen above and write down what you would ask to confirm before it.
Technical Evaluation
reportedDeeper technical assessments to evaluate your problem-solving skills.
What to demonstrate
- Deeper technical assessments to evaluate your problem-solving skills
- Depth in Software Engineering (General)
How to prepare
- Answer aloud and timed: Walk me through your career progression over the last decade and explain the key turning points.
- Answer aloud and timed: How did the engineering culture at your previous companies shape your current approach to software development?
Cultural Fit Assessment
reportedDiscussion to assess alignment with Hazel Health's healthcare mission.
What to demonstrate
- Discussion to assess alignment with Hazel Health's healthcare mission
- Depth in Software Engineering (General)
How to prepare
- Answer aloud and timed: Tell me about a time you had to work with an unstructured or ambiguous set of requirements.
- Answer aloud and timed: How do you handle situations where your technical recommendations are met with skepticism by non-technical stakeholders?
Final Offer Stage
reportedDiscussion regarding the final offer and terms of employment.
What to demonstrate
- Discussion regarding the final offer and terms of employment
- Depth in Software Engineering (General)
How to prepare
- Answer aloud and timed: Describe a time when you had to adapt quickly to a sudden change in project scope or company priorities.
- Work Software Engineering (General) until you can explain it without notes
PracHub editorial advice for the preparation topics above.
Know your resume inside out
Be ready to discuss projects, technologies, and decisions from any point in your career, even those dating back more than seven years. Do not assume interviewers will only focus on your most recent role.
Emphasize your empathy
Because Hazel Health operates in the pediatric mental and physical health space, demonstrating a genuine care for the end-user is just as important as your coding ability.
Prepare for varied interview styles
You may encounter interviewers who are highly structured, as well as those who are more conversational or less prepared. Remain professional, structured, and proactive in highlighting your technical achievements regardless of the interviewer's style.
Some candidates have reported encountering unstructured or rapid-fire resume questioning during hiring manager screens
Stay patient, keep your answers concise, and gently guide the conversation toward your relevant technical achievements.
Choose a category, try a prompt, then open its approach, worked solution or follow-up when you need it.
Canonicalise a request body into a stable idempotency fingerprint
idempotency_key.request_fingerprint is a SHA-256 over the method, path and canonicalised body, and a retry whose fingerprint differs must be rejected with 422 rather than served the stored response. Write the canonicaliser. Bodies are JSON up to 256 KB nested at most 32 levels; clients vary key order, whitespace and unicode escaping, and some send 64-bit ids as JSON numbers. Produce a deterministic byte string such that semantically identical bodies match and any semantic difference does not. State your complexity and name two normalisations you refuse to perform.
Approach
- Parse once into a tree, then re-serialise under fixed rules: object keys sorted, array order preserved, one escaping convention, no insignificant whitespace. Parsing is O(n) and sorting keys is O(k log k) per object, so O(n log n) overall with O(depth) stack, and the 32-level cap is enforced during parsing because hostile nesting is how a canonicaliser becomes a stack overflow.
- Sort keys by their UTF-8 bytes and say why the obvious implementation is wrong in some runtimes: a default string comparison that orders by UTF-16 code units places surrogate pairs, meaning code points from U+10000 up, below U+E000 to U+FFFF, which is not UTF-8 byte order, so two services written in different languages disagree on the same document.
- Do not re-encode numbers through a double. IEEE-754 binary64 represents integers exactly only up to 2^53, so normalising a 19-digit id through a float changes it, and 1 against 1.0 cannot be reconciled without deciding whether they are the same value. Preserve the literal token, and require ids as strings at the API boundary if you want them comparable.
- Reject duplicate keys rather than picking one. JSON permits them and parsers disagree, most keeping the last, so any choice you make ties the fingerprint to a parser detail that the code handling the request does not necessarily share.
Follow-up
- A client sends the same logical request with an extra field your API ignores. Same key, different fingerprint, so you return 422. Is that the right answer?
- Where does the fingerprint get computed relative to request decompression and the body-size limit?
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?
Merge partitioned event streams into one ordered feed with bounded lateness
The read-model service consumes 64 log partitions carrying about 4,000 events per second in total. Each partition is ordered within itself, but partitions drift by up to 30 seconds, and the activity feed must present a tenant's events in occurred_at order. Produce the merge. State its complexity, the buffer it requires in events and in bytes, what happens when one partition is idle, and what you do with an event that arrives after you have already emitted its position. Payloads average 1 KB.
Approach
- Merge with a min-heap over the 64 partition heads keyed on (occurred_at, event_id): O(log P) per event and O(n log P) overall. The tie-break on event_id is what makes the output deterministic when two partitions carry the same millisecond, which matters because the feed is paginated and a non-deterministic order reorders pages under the reader.
- Emitting the heap head is only correct once every partition has produced everything up to that timestamp, so the emit condition is a watermark: the minimum across partitions of the highest occurred_at seen, less the allowed lateness. Events are held until the watermark passes them, which is what turns individually ordered streams into a jointly ordered one.
- Size the buffer from the lateness rather than guessing: 4,000 events per second times 30 seconds is 120,000 buffered events, and at 1 KB each about 120 MB of heap. That number is the real price of the ordering guarantee and belongs in front of whoever asked for it.
- Handle the idle partition explicitly, because it fails the feed rather than corrupting it: a partition with no traffic never advances its own maximum, so the watermark freezes and output stops entirely. Either every partition emits a periodic idle marker carrying the broker's current time, or the watermark falls back to wall clock for a partition silent beyond a threshold.
Follow-up
- The lateness budget is raised to five minutes. What is the new buffer, and what besides memory changes?
- The consumer restarts. Where does it resume from, and what does the feed look like for the first 30 seconds?
Keep soft-deleted accounts from blocking re-registration
app_user holds user_id, tenant_id, email CITEXT, password_hash (NULL for SSO principals), email_verified_at, auth_version, status ('invited','active','suspended','deactivated'), created_at, updated_at, deleted_at. Two live accounts for one address inside a tenant must be impossible, but an address freed by a soft delete must be reusable, and the same tenant may delete and re-register it repeatedly. Write the uniqueness DDL for PostgreSQL 16, then the equivalent for MySQL 8 where partial indexes do not exist, and say what each permits once three deleted rows already hold that address.
Approach
- Start from what is actually unique: not (tenant_id, email), but (tenant_id, email) among live rows. PostgreSQL says that directly — CREATE UNIQUE INDEX app_user_live_email ON app_user (tenant_id, email) WHERE deleted_at IS NULL. A full constraint over the same two columns burns the address permanently the first time someone deletes an account.
- Keep case-insensitivity in the type or the index, never in the application: CITEXT as given, or UNIQUE (tenant_id, lower(email)) as an expression index where the extension is unavailable. A case-sensitive unique column is exactly how two accounts for one human appear.
- For MySQL 8 the predicate has to move inside the key: add a discriminator column that is a constant 0 while the row is live and is set to user_id on delete, with UNIQUE (tenant_id, email, deleted_marker). Live rows share the constant and still collide; deleted rows differ from each other and stop colliding.
- State the NULL variant and its dependency: leaving the marker NULL for deleted rows also works, because a unique index treats NULLs as distinct — true in MySQL, and true in PostgreSQL only under the default NULLS DISTINCT, which PostgreSQL 15 lets you reverse. Check the polarity against the three existing deleted rows: constant-on-live is what preserves the collision you want, and reversing it silently admits duplicate live accounts.
Follow-up
- A deleted account re-registers with the same address the next day. Do the old resource rows follow the new user_id, and how does the API keep the two principals apart?
- How do you honour an erasure request while resource_revision.actor_user_id still references this table?
Replace offset paging on the resource feed with keyset
resource holds resource_id, tenant_id, owner_user_id, title, body_ref, version, status ('draft','active','archived','deleted'), created_at, updated_at, deleted_at, with an index on (tenant_id, status, updated_at DESC, resource_id DESC). The listing endpoint returns active resources for one tenant, newest update first, 50 per page, today with LIMIT 50 OFFSET n. Tenants reach page 400 and rows are created while they read. Write the keyset query, define what the cursor carries and how it is encoded, and say which part of the index each predicate uses. Assume PostgreSQL 16.
Approach
- Name the two failures separately. OFFSET 20000 makes the server produce and discard 20,000 rows, so page cost grows with depth rather than with page size. Independently, any write that changes how many rows sort above the offset moves the window between two fetches, and the direction decides which anomaly you get: an insert lands at the head of updated_at DESC and pushes already-returned rows down past the boundary, so they are returned a second time; a delete above the offset, or a row whose updated_at is bumped above the cursor, pulls rows up and one is never returned at all. Nothing in the response reveals either.
- Write the seek: WHERE tenant_id = $1 AND status = 'active' AND (updated_at, resource_id) < ($2, $3) ORDER BY updated_at DESC, resource_id DESC LIMIT 50. The row-value comparison is one index range rather than a disjunction, and both columns are NOT NULL, which is what makes that comparison well defined.
- Map each predicate onto the index: tenant_id and status are equality on the leading columns, (updated_at, resource_id) is the range, and the ORDER BY matches the index order so no Sort node appears and the scan stops after 50 rows. The DESC in the definition only matters for mixed directions — a plain ascending btree on the same columns is read backwards for this query.
- Put both sort columns in the cursor and nothing the client can tamper with into another tenant: base64 of (updated_at, resource_id), validated server-side, with tenant_id taken from the principal.
Follow-up
- The client asks for 'jump to page 400'. What do you offer instead, and what does the honest version cost?
- Sort order becomes user-selectable across four columns. How many indexes is that, and which would you refuse to add?
Did you cry a lot when you watched the movie E.T.?
Did you cry a lot when you watched the movie E.T.?
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 motivates you to work in the pediatric healthcare space?
What motivates you to work in the pediatric healthcare space?
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?
Why did you choose to work at [Company Name] over seven years ago, and what did you learn from that environmen
Why did you choose to work at [Company Name] over seven years ago, and what did you learn from that environment?
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 career progression over the last decade and explain the key turning points.
Walk me through your career progression over the last decade and explain the key turning points.
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 did the engineering culture at your previous companies shape your current approach to software development
How did the engineering culture at your previous companies shape your current approach to software development?
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?
p99 jumped on one listing filter while p50 stayed flat
After a release that added an owner_user_id filter to the resource listing, p99 rose from 90 ms to 1.9 s while p50 stayed at 40 ms. Traffic and row counts are unchanged. resource carries the index (tenant_id, status, updated_at DESC, resource_id DESC). The new query filters tenant_id and owner_user_id, orders by updated_at DESC, resource_id DESC, and takes 20 rows. On PostgreSQL, explain the shape of the regression, prove it from a query plan, and give the index you would add.
Approach
- Start from the shape. A flat p50 with a moved p99 means a subset of requests changed cost, not all of them, so the first job is naming the subset. Bucket the endpoint's latency by the tenant's row count; the natural hypothesis is that large tenants are a small share of requests and all of the tail.
- Get the plan for the new query on a large tenant with EXPLAIN (ANALYZE, BUFFERS). Expect an index scan over the tenant's range, a filter discarding most of it, then a Sort feeding the Limit, possibly reporting Sort Method: external merge Disk. Read actual rows on the scan node, not estimated.
- Explain why the existing index cannot serve it. A composite B-tree is seekable only as a left prefix, and with no equality predicate on status the scan cannot treat updated_at as an ordering, because rows in the tenant's range are ordered by status first. Everything matching must be read and sorted before LIMIT 20 can apply, so a tenant with 400,000 rows pays 400,000 rows to return 20.
- Add (tenant_id, owner_user_id, updated_at DESC, resource_id DESC). Equality on the first two columns leaves the index ordered by updated_at within that pair, so the plan becomes an index scan that stops after 20 rows with no Sort node. PostgreSQL can scan a B-tree backwards, so the DESC markers matter only if the two sort columns ever disagree in direction; keeping them explicit documents the order the keyset cursor depends on.
Follow-up
- The endpoint paginates with OFFSET. What does page 500 cost with your index, and what does the keyset version cost?
- How would you have caught this before release, given that a 10,000-row seed database produces the same plan shape at an unnoticeable cost?
Built from the rounds and topics Hazel Health candidates report.
Prepare, practise & reflect
One practical outcome each day. Spend longer where you need it.
0 / 7 done01Map the Hazel Health loop
- Write out the reported sequence: Application Review, Behavioral Screen, Technical Evaluation, Cultural Fit Assessment, Final Offer Stage.
- 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 5 reported rounds, with the weakest marked.
02Work Software Engineering (General)
- Spend the session on Software Engineering (General), which Hazel Health candidates report being tested on.
- Write one worked example in Software Engineering (General) and time yourself on it.
Deliverable: One timed worked example in Software Engineering (General).
03Work Data Privacy & Security (Healthcare)
- Spend the session on Data Privacy & Security (Healthcare), which Hazel Health candidates report being tested on.
- Write one worked example in Data Privacy & Security (Healthcare) and time yourself on it.
Deliverable: One timed worked example in Data Privacy & Security (Healthcare).
04Work Healthcare Software (Domain-Specific)
- Spend the session on Healthcare Software (Domain-Specific), which Hazel Health candidates report being tested on.
- Write one worked example in Healthcare Software (Domain-Specific) and time yourself on it.
Deliverable: One timed worked example in Healthcare Software (Domain-Specific).
05Answer out loud: Conversational & Icebreaker Questions
- Answer aloud, timed: Did you cry a lot when you watched the movie E.T.?
- Answer aloud, timed: What motivates you to work in the pediatric healthcare space?
Deliverable: Spoken answers to 2 reported Conversational & Icebreaker Questions question(s), under time.
06Answer out loud: Resume & Professional History Deep Dives
- Answer aloud, timed: Why did you choose to work at [Company Name] over seven years ago, and what did you learn from that environment?
- Answer aloud, timed: Walk me through your career progression over the last decade and explain the key turning points.
Deliverable: Spoken answers to 2 reported Resume & Professional History Deep Dives question(s), under time.
07Answer out loud: Behavioral & Situational Questions
- Answer aloud, timed: Tell me about a time you had to work with an unstructured or ambiguous set of requirements.
- Answer aloud, timed: How do you handle situations where your technical recommendations are met with skepticism by non-technical stakeholders?
Deliverable: Spoken answers to 2 reported Behavioral & Situational 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.
Tell me about a non-technical passion or hobby that keeps you grounded outside of work.
Tell me about a non-technical passion or hobby that keeps you grounded outside of work.
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 work with an unstructured or ambiguous set of requirements.
Tell me about a time you had to work with an unstructured or 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?
How do you handle situations where your technical recommendations are met with skepticism by non-technical sta
How do you handle situations where your technical recommendations are met with skepticism by non-technical stakeholders?
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 when you had to adapt quickly to a sudden change in project scope or company priorities.
Describe a time when you had to adapt quickly to a sudden change in project scope or company priorities.
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
Tell me about a non-technical passion or hobby that keeps you grounded outside of work.
- 02
Tell me about a time you had to work with an unstructured or ambiguous set of requirements.
- 03
How do you handle situations where your technical recommendations are met with skepticism by non-technical stakeholders?
- 04
Describe a time when you had to adapt quickly to a sudden change in project scope or company priorities.
How technical is the initial interview stage?
The initial interview with the hiring manager can often be highly conversational and focused on your resume history rather than immediate coding challenges. Be prepared to discuss your past roles in detail, even those from several years ago, before moving into deeper technical rounds.
Hazel Health Software Engineer candidate reports ↗What is the company culture like for engineers?
The culture is highly mission-driven and collaborative. Engineers work closely with clinical teams, which requires a high degree of empathy and a strong focus on user experience, as the end-users are often school children, parents, and therapists.
Hazel Health Software Engineer candidate reports ↗How should I handle highly unconventional or casual questions?
Embrace them with authenticity and humor. Interviewers at Hazel Health sometimes use disarming questions to break the ice and assess your natural conversational style. Staying relaxed and genuine is highly valued.
Hazel Health Software Engineer candidate reports ↗Is remote work supported for this position?
Yes, Hazel Health offers remote opportunities for many of its engineering roles, though some positions may have location preferences depending on team alignment and local state regulations.
Hazel Health Software Engineer candidate reports ↗What topics does Hazel Health test in interviews?
Hazel Health interviews most often cover Stakeholder Management, Solutions Consulting, Software Engineering (General), Scenario-Based Problem Solving, and Case Study Presentation. The exact emphasis depends on the specific role you apply for.
Hazel 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.
- 01Hazel 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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