As a Software Engineer at Heartflow, you play a pivotal role in the development and enhancement of innovative medical imaging solutions that directly impact patient care. Your work contributes to the creation of advanced technologies that help clinicians assess cardiovascular health, enabling personalized patient management. This position is not only crucial for the technical development of our products but also for improving health outcomes for patients around the world. The Software Engineer role at Heartflow involves addressing complex challenges that require a blend of creativity and technical expertise. You will collaborate with cross-functional teams to implement robust software solutions that are both scalable and reliable. Engaging with cutting-edge technologies, you will be at the forefront of transforming how medical data is processed and utilized, making this position both strategic and rewarding. Working within a dynamic environment, you will have the opportunity to contribute to projects that involve image processing and machine learning, among others. This role is critical as it supports the company’s mission to revolutionize cardiovascular diagnostics, making it an exciting opportunity for passionate and skilled engineers.
Initial Screening
reportedCandidates undergo preliminary assessments to evaluate their fit for the role.
What to demonstrate
- Candidates undergo preliminary assessments to evaluate their fit for the role
- Depth in C++ Programming
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.
Technical Assessment
reportedCandidates participate in technical evaluations to assess their problem-solving capabilities.
What to demonstrate
- Candidates participate in technical evaluations to assess their problem-solving capabilities
- Depth in C++ Programming
How to prepare
- Answer aloud and timed: What are the performance implications of various data structures in C++?
- Answer aloud and timed: How would you approach optimizing a given piece of code?
Behavioral Interview
reportedInterviews focus on assessing cultural fit and teamwork skills through behavioral questions.
What to demonstrate
- Interviews focus on assessing cultural fit and teamwork skills through behavioral questions
- Depth in C++ Programming
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 interview above and write down what you would ask to confirm before it.
Engagement with Team Members
reportedOpportunities for candidates to interact with team members and learn about the company culture.
What to demonstrate
- Opportunities for candidates to interact with team members and learn about the company culture
- Depth in C++ Programming
How to prepare
- Answer aloud and timed: Provide a solution for a hypothetical case involving data inconsistency in a medical imaging application.
- Answer aloud and timed: Walk us through your thought process when debugging a complex software issue.
PracHub editorial advice for the preparation topics above.
Practice coding on a whiteboard
This helps simulate the interview environment and improve your problem-solving visibility.
Familiarize yourself with medical imaging concepts
Understanding the domain can significantly enhance your discussions during interviews.
Be prepared to ask insightful questions
This shows your genuine interest in the role and helps you assess if Heartflow aligns with your career goals.
Choose a category, try a prompt, then open its approach, worked solution or follow-up when you need it.
Explain the concepts of garbage collection and memory management.
Explain the concepts of garbage collection and memory management.
Approach
- Say what the runtime actually does before reasoning about the code.
- Name what is shared across threads and what owns each piece of state.
- Identify the window where an invariant is briefly untrue.
- Distinguish a value from a reference to it, and say which one you handed out.
Follow-up
- What happens if two callers reach this at the same time?
- Where could this allocate more than you expect?
Write a function in Python to reverse a linked list.
Write a function in Python to reverse a linked list.
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 graph problem and explain your approach.
Solve a graph problem and explain your approach.
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?
Discuss the time complexity of your solution.
Discuss the time complexity of your solution.
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?
Denormalise tenant onto revisions and backfill it live
resource_revision (revision_id, resource_id, version, actor_user_id, change_kind, patch, request_id, created_at) has 400M rows and no tenant column; tenant_id lives only on resource. Two reads need it: a tenant-scoped audit feed ordered by created_at DESC, and an offboarding purge. Both join back to resource today. Justify adding tenant_id to resource_revision against those two reads, name the anomaly the copy introduces and the constraint that prevents it, then give the ordered migration for a live table taking 1.2k writes/second — the lock each step takes, how the backfill is batched, and where each step stops being reversible. PostgreSQL 16.
Approach
- Justify from the access path rather than from taste. Without the column, the audit feed either scans resource_revision by created_at and discards other tenants' rows, or resolves the tenant's resource_ids first and probes with them — both proportional to the tenant's whole history rather than to one page. With (tenant_id, created_at DESC, revision_id DESC) it is a seek that stops at 50 rows, and the purge becomes a ranged delete instead of a join.
- Name the cost exactly: a second copy of a fact can disagree with the first. Make the disagreement unwritable rather than documented — add UNIQUE (resource_id, tenant_id) on resource so it can serve as a foreign-key target, then FOREIGN KEY (resource_id, tenant_id) REFERENCES resource (resource_id, tenant_id) on the revision table. A revision can then only ever carry its parent's tenant.
- Step one, expand: ALTER TABLE resource_revision ADD COLUMN tenant_id BIGINT NULL, with no default, so it is a catalogue change and no rewrite. It still needs ACCESS EXCLUSIVE for an instant, and that instant queues behind the longest open transaction on the table while every later query queues behind it — set lock_timeout to 2s and retry rather than wait.
- Step two, dual-write: deploy the writer that populates tenant_id on every new revision while reads still use the join. Reversible by redeploying the previous build, because nothing reads the column yet.
Follow-up
- The backfill is half finished and a rollback is required. What state is the table in, and what does the previous build do with a half-populated column?
- How do you verify the backfill actually finished, given rows are still being inserted while it runs?
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?
Describe different machine learning techniques such as Expectation-Maximization (EM) and Hidden Markov Models
Describe different machine learning techniques such as Expectation-Maximization (EM) and Hidden Markov Models (HMMs).
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 are the performance implications of various data structures in C++?
What are the performance implications of various data structures in C++?
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 approach optimizing a given piece of code?
How would you approach optimizing a given piece of 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?
Discuss the advantages and disadvantages of using OpenMP for parallel programming.
Discuss the advantages and disadvantages of using OpenMP for parallel programming.
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 handle a situation where a system performance issue arises unexpectedly?
How would you handle a situation where a system performance issue arises unexpectedly?
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?
Provide a solution for a hypothetical case involving data inconsistency in a medical imaging application.
Provide a solution for a hypothetical case involving data inconsistency in a medical imaging application.
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 thought process when debugging a complex software issue.
Walk us through your thought process when debugging a complex software 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 Heartflow candidates report.
Prepare, practise & reflect
One practical outcome each day. Spend longer where you need it.
0 / 7 done01Map the Heartflow loop
- Write out the reported sequence: Initial Screening, Technical Assessment, Behavioral Interview, Engagement with Team Members.
- 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 C++ Programming
- Spend the session on C++ Programming, which Heartflow candidates report being tested on.
- Write one worked example in C++ Programming and time yourself on it.
Deliverable: One timed worked example in C++ Programming.
03Work Performance Engineering
- Spend the session on Performance Engineering, which Heartflow candidates report being tested on.
- Write one worked example in Performance Engineering and time yourself on it.
Deliverable: One timed worked example in Performance Engineering.
04Work Time Complexity Analysis
- Spend the session on Time Complexity Analysis, which Heartflow candidates report being tested on.
- Write one worked example in Time Complexity Analysis and time yourself on it.
Deliverable: One timed worked example in Time Complexity Analysis.
05Answer out loud: Technical / Domain Questions
- Answer aloud, timed: Explain the concepts of garbage collection and memory management.
- Answer aloud, timed: Describe different machine learning techniques such as Expectation-Maximization (EM) and Hidden Markov Models (HMMs).
Deliverable: Spoken answers to 2 reported Technical / Domain Questions question(s), under time.
06Answer out loud: Problem-Solving / Case Studies
- Answer aloud, timed: How would you handle a situation where a system performance issue arises unexpectedly?
- Answer aloud, timed: Provide a solution for a hypothetical case involving data inconsistency in a medical imaging application.
Deliverable: Spoken answers to 2 reported Problem-Solving / Case Studies question(s), under time.
07Answer out loud: Behavioral / Leadership
- Answer aloud, timed: Describe a challenging project you worked on. What role did you play, and what was the outcome?
- Answer aloud, timed: How do you prioritize tasks when faced with multiple deadlines?
Deliverable: Spoken answers to 2 reported Behavioral / Leadership 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 challenging project you worked on. What role did you play, and what was the outcome?
Describe a challenging project you worked on. What role did you play, and what was the outcome?
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 faced with multiple deadlines?
How do you prioritize tasks when faced with multiple deadlines?
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?
Can you give an example of how you handled conflict within a team?
Can you give an example of how you handled conflict within a team?
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 challenging project you worked on. What role did you play, and what was the outcome?
- 02
How do you prioritize tasks when faced with multiple deadlines?
- 03
Can you give an example of how you handled conflict within a team?
What is the typical timeline from the initial screen to an offer?
The interview process typically spans several weeks, depending on scheduling and the number of interview rounds. Candidates can expect timely communication from the recruitment team throughout.
Heartflow Software Engineer candidate reports ↗How much preparation time is recommended?
Aim for at least two to four weeks of focused preparation, allowing you to review core technical concepts and practice coding problems.
Heartflow Software Engineer candidate reports ↗What differentiates successful candidates?
Successful candidates are those who not only have strong technical skills but also demonstrate effective communication and collaboration during the interview process.
Heartflow Software Engineer candidate reports ↗What is the company culture like at Heartflow?
Heartflow fosters a collaborative and innovative environment where employees are encouraged to contribute ideas and work together towards a common goal of improving patient care.
Heartflow Software Engineer candidate reports ↗What topics does Heartflow test in interviews?
Heartflow interviews most often cover C++ Programming, Python, Communication Skills, Performance Engineering, and QA Engineer Testing Fundamentals. The exact emphasis depends on the specific role you apply for.
Heartflow 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.
- 01Heartflow 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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