A Software Engineer at Catalyst Labs plays a crucial role in developing innovative solutions that enhance healthcare delivery. This position is pivotal as it directly impacts how users interact with our products, which aim to improve patient outcomes and streamline healthcare processes. Software Engineers are tasked with creating scalable, efficient, and reliable applications that serve the needs of healthcare professionals and organizations, making their work both technically challenging and deeply rewarding. In this role, you will engage with complex systems and collaborate with cross-functional teams, including product managers, designers, and data scientists. This collaborative environment allows you to influence product direction and contribute to projects that have real-world implications. Expect a dynamic work atmosphere where your technical skills and problem-solving abilities will be put to the test, ultimately shaping the future of healthcare technology.
Phone Screening
reportedInitial call to evaluate candidate's background and role fit.
What to demonstrate
- Initial call to evaluate candidate's background and role fit
- Depth in AngularJS
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.
Take-Home Coding Assignment
reportedCandidates complete a coding task to demonstrate technical skills.
What to demonstrate
- Candidates complete a coding task to demonstrate technical skills
- Depth in AngularJS
How to prepare
- Answer aloud and timed: Describe the principles of Object-Oriented Programming.
- Answer aloud and timed: What is dependency injection, and how is it implemented?
Onsite/Virtual Interviews
reportedMultiple interviews assessing technical abilities and cultural fit.
What to demonstrate
- Multiple interviews assessing technical abilities and cultural fit
- Depth in AngularJS
How to prepare
- Answer aloud and timed: Can you discuss your experience with cloud services like AWS or Azure?
- Answer aloud and timed: Write a function to reverse a linked list.
PracHub editorial advice for the preparation topics above.
Know Your Technologies
Be prepared to discuss specific technologies you have experience with, especially those mentioned in the job description. Demonstrating depth in these areas can significantly boost your candidacy.
Practice Coding
Spend time practicing coding problems, particularly those related to data structures and algorithms. Platforms like LeetCode or HackerRank can be invaluable for this purpose.
Engage with Interviewers
Use the interview as a two-way conversation. Ask questions about the team, projects, and company culture to establish rapport and show genuine interest.
Be Authentic
While it’s important to align with company values, don’t compromise your authenticity. Showcase your personality and how it fits within the Catalyst Labs culture.
Choose a category, try a prompt, then open its approach, worked solution or follow-up when you need it.
Write a function to reverse a linked list.
Write a function 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?
How would you find the longest substring without repeating characters?
How would you find the longest substring without repeating characters?
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?
Describe how to implement a binary search algorithm.
Describe how to implement a binary search algorithm.
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 problem using dynamic programming techniques.
Solve a problem using dynamic programming techniques.
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?
Write a SQL query to find the second highest salary in a table.
Write a SQL query to find the second highest salary in a table.
Approach
- Name the grain you start from and join outward from it.
- Check whether any join is one-to-many before aggregating, or the sums inflate.
- Say which index the query would use, and what makes it unusable.
- Handle the rows that do not match: that is usually the actual question.
Follow-up
- How does the query change if that join becomes one-to-many?
- What happens to this when the table is ten times larger?
Explain why the owner filter ignores the listing index
The only index on resource is (tenant_id, status, updated_at DESC, resource_id DESC). A new endpoint returns one user's resources across all statuses, newest created first: WHERE tenant_id = $1 AND owner_user_id = $2 ORDER BY created_at DESC LIMIT 20. On a tenant with 2M rows it takes 900 ms and EXPLAIN shows a sort above a large scan. Explain precisely why the existing index cannot serve it, give the index that can, and state which of these the new index still will not help: owner_user_id alone across tenants; the same query ordered by updated_at. PostgreSQL 16.
Approach
- Separate the two jobs an index does. For filtering, a composite btree is seekable only on a left prefix, so with no predicate on status the scan can at best range over tenant_id and test owner_user_id per row; PostgreSQL 16 has no btree skip scan to jump the unconstrained column.
- For ordering, the index is sorted by (status, updated_at) within a tenant and not by created_at, so the LIMIT cannot stop early: every matching row is read and then sorted. That is the 'Sort Method: top-N heapsort' line, and it is why the plan reads 2M rows to answer with 20.
- Derive the replacement from the access path — equality, equality, then the ordering column: CREATE INDEX CONCURRENTLY ON resource (tenant_id, owner_user_id, created_at DESC). The scan seeks to the (tenant, owner) range and walks 20 entries in order, so the Sort node disappears along with the row-read.
- Treat INCLUDE (title, status) as conditional, not free. An index-only scan still visits the heap for any row whose page is not marked all-visible, so on a table taking 1.2k writes/second the win depends on autovacuum keeping the visibility map current, and the wider index costs more on every insert.
Follow-up
- 90% of rows are status='active'. Would a partial index WHERE status = 'active' change your answer, and for which of the three queries?
- A dashboard runs this for 40 owners in one page load. What changes about the design?
Explain the differences between REST and SOAP web services.
Explain the differences between REST and SOAP web services.
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?
Describe the principles of Object-Oriented Programming.
Describe the principles of Object-Oriented 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?
What is dependency injection, and how is it implemented?
What is dependency injection, and how is it implemented?
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 design a URL shortening service?
How would you design a URL shortening service?
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 considerations would you take into account when designing a scalable database?
What considerations would you take into account when designing a scalable database?
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?
Discuss how to ensure high availability in a microservices architecture.
Discuss how to ensure high availability in a microservices architecture.
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 approach designing a messaging system?
How would you approach designing a messaging system?
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 factors influence your choice of database technology for an application?
What factors influence your choice of database technology for an 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?
Given a set of requirements, how would you approach developing a new feature?
Given a set of requirements, how would you approach developing a new feature?
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 estimate the time required to complete a project?
How would you estimate the time required to complete a 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?
Describe how you would handle a performance bottleneck in an application.
Describe how you would handle a performance bottleneck in an 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?
What strategies do you use for testing and validating your code?
What strategies do you use for testing and validating your 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?
Walk me through your thought process for debugging a production issue.
Walk me through your thought process for debugging a production issue.
Approach
- Establish what changed and when, before forming any theory.
- Pick a bisection that eliminates candidates whichever way it turns out.
- Check the instrumentation before believing the symptom.
- Separate the trigger from the cause; the deploy is rarely the bug.
Follow-up
- What would you look at first, and what would it rule out?
- How would you tell a cause from a coincidence here?
Built from the rounds and topics Catalyst Labs candidates report.
Prepare, practise & reflect
One practical outcome each day. Spend longer where you need it.
0 / 7 done01Map the Catalyst Labs loop
- Write out the reported sequence: Phone Screening, Take-Home Coding Assignment, Onsite/Virtual Interviews.
- 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 AngularJS
- Spend the session on AngularJS, which Catalyst Labs candidates report being tested on.
- Write one worked example in AngularJS and time yourself on it.
Deliverable: One timed worked example in AngularJS.
03Work Entity Framework
- Spend the session on Entity Framework, which Catalyst Labs candidates report being tested on.
- Write one worked example in Entity Framework and time yourself on it.
Deliverable: One timed worked example in Entity Framework.
04Work C#
- Spend the session on C#, which Catalyst Labs candidates report being tested on.
- Write one worked example in C# and time yourself on it.
Deliverable: One timed worked example in C#.
05Answer out loud: Technical / Domain Questions
- Answer aloud, timed: Explain the differences between REST and SOAP web services.
- Answer aloud, timed: How do you handle version control in your projects?
Deliverable: Spoken answers to 2 reported Technical / Domain Questions question(s), under time.
06Answer out loud: Coding / Algorithms
- Answer aloud, timed: Write a function to reverse a linked list.
- Answer aloud, timed: How would you find the longest substring without repeating characters?
Deliverable: Spoken answers to 2 reported Coding / Algorithms question(s), under time.
07Answer out loud: Behavioral / Leadership
- Answer aloud, timed: Tell me about a time you faced a challenge in a project. How did you handle it?
- Answer aloud, timed: How do you prioritize tasks when working on multiple projects simultaneously?
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.
How do you handle version control in your projects?
How do you handle version control in your 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?
Can you discuss your experience with cloud services like AWS or Azure?
Can you discuss your experience with cloud services like AWS or Azure?
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 faced a challenge in a project. How did you handle it?
Tell me about a time you faced a challenge in a project. How did you handle it?
Approach
- Pick a story where you made the decision, not one where you watched it.
- State the situation in two sentences and spend the rest on the reasoning.
- Give the blast radius: what could have broken, and what you measured.
- Name the disagreement and how you resolved it with evidence.
Follow-up
- What would you do differently if you ran that again?
- How did you know your change caused the improvement?
How do you prioritize tasks when working on multiple projects simultaneously?
How do you prioritize tasks when working on multiple projects simultaneously?
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 situation where you had to collaborate with a difficult team member.
Describe a situation where you had to collaborate with a difficult team member.
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 work in the software engineering field?
What motivates you to work in the software engineering field?
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 keep up with the latest technology trends?
How do you keep up with the latest technology trends?
Approach
- Pick a story where you made the decision, not one where you watched it.
- State the situation in two sentences and spend the rest on the reasoning.
- Give the blast radius: what could have broken, and what you measured.
- Name the disagreement and how you resolved it with evidence.
Follow-up
- What would you do differently if you ran that again?
- How did you know your change caused the improvement?
- 01
How do you handle version control in your projects?
- 02
Can you discuss your experience with cloud services like AWS or Azure?
- 03
Tell me about a time you faced a challenge in a project. How did you handle it?
- 04
How do you prioritize tasks when working on multiple projects simultaneously?
What is the difficulty level of the interviews?
The interviews are generally considered average to challenging, depending on the specific team and role. Candidates should expect a mix of technical and behavioral questions tailored to assess both skills and cultural fit.
Catalyst Labs Software Engineer candidate reports ↗How much preparation time is typical?
Candidates often spend several weeks preparing for the interview process, focusing on coding challenges, system design, and behavioral questions. Tailor your preparation based on the specific requirements of the role.
Catalyst Labs Software Engineer candidate reports ↗What differentiates successful candidates?
Successful candidates typically demonstrate a strong technical foundation, excellent problem-solving abilities, and an alignment with the company culture. Being able to articulate your thought process and experiences will also set you apart.
Catalyst Labs Software Engineer candidate reports ↗What is the company culture like at Catalyst Labs?
Catalyst Labs fosters a collaborative and innovative environment where employees are encouraged to contribute ideas and work together towards common goals. Expect a focus on continuous improvement and a commitment to making a positive impact in healthcare.
Catalyst Labs Software Engineer candidate reports ↗How long does the interview process usually take?
The interview process can take several weeks, depending on scheduling and the number of candidates. Communication may vary, so it’s advisable to follow up if you have not received updates.
Catalyst Labs Software Engineer candidate reports ↗Is remote work an option?
Remote work policies may vary by team and role. Be sure to clarify expectations regarding remote or hybrid work arrangements during your interview.
Catalyst Labs Software Engineer candidate reports ↗What topics does Catalyst Labs test in interviews?
Catalyst Labs interviews most often cover SQL, Stakeholder Management, SQL Query Writing, Stakeholder Communication, and Subqueries. The exact emphasis depends on the specific role you apply for.
Catalyst Labs 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.
- 01Catalyst Labs 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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