As a Software Engineer at Charles River Laboratories, you play a pivotal role in developing and maintaining software solutions that support critical processes in the life sciences sector. This position is essential for driving innovation, improving operational efficiencies, and ensuring compliance with industry standards. Your contributions will directly influence the development of products that enhance research and development in biopharmaceuticals, ultimately impacting patient health and safety. In this role, you will work on complex systems that require a blend of technical expertise and problem-solving skills. You will collaborate with cross-functional teams, including scientists, product managers, and other engineers, to design software that meets the evolving needs of our clients. With the rapid advancements in technology and the increasing demand for data-driven insights in life sciences, your work will be both challenging and rewarding, allowing you to make a significant impact on the industry.
Phone Screen
reportedInitial phone screen with a recruiter to discuss your background and role fit.
What to demonstrate
- Initial phone screen with a recruiter to discuss your background and role fit
- Depth in Programmable Logic Control (PLC)
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 Interviews
reportedInterviews with hiring managers focusing on technical skills and problem-solving abilities.
What to demonstrate
- Interviews with hiring managers focusing on technical skills and problem-solving abilities
- Depth in Programmable Logic Control (PLC)
How to prepare
- Answer aloud and timed: Describe a challenging technical problem you solved in a previous project.
- Answer aloud and timed: How do you approach debugging an application?
PracHub editorial advice for the preparation topics above.
Be prepared to discuss your past projects
Have concrete examples ready to illustrate your technical skills and problem-solving abilities.
Demonstrate your passion for the life sciences
Show how your interests align with the mission of Charles River Laboratories.
Practice coding problems
Familiarize yourself with common algorithms and data structures to prepare for technical interviews.
Ask insightful questions
Prepare thoughtful questions for your interviewers to demonstrate your interest in the role and company.
Choose a category, try a prompt, then open its approach, worked solution or follow-up when you need it.
Can you walk us through your thought process for optimizing an algorithm?
Can you walk us through your thought process for optimizing an 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?
Write a function to reverse a string in your preferred programming language.
Write a function to reverse a string in your preferred programming language.
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 implement a binary search algorithm?
How would you 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?
Can you explain the differences between stack and queue data structures?
Can you explain the differences between stack and queue data structures?
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 method to detect if a linked list has a cycle.
Write a method to detect if a linked list has a cycle.
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?
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?
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?
What programming languages are you most proficient in, and why?
What programming languages are you most proficient in, and why?
Approach
- Clarify what is being asked and what a complete answer contains.
- State your assumptions explicitly before working the problem.
- Say what you would check first and why it is the highest-information step.
- Work from the requirement backwards to the design.
Follow-up
- What assumption would you test first?
- How would you know your answer was wrong?
Can you explain the concept of object-oriented programming?
Can you explain the concept 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?
Describe a challenging technical problem you solved in a previous project.
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?
What are the best practices for writing maintainable code?
What are the best practices for writing maintainable 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 approach designing a software system for managing laboratory data?
How would you approach designing a software system for managing laboratory data?
Approach
- Clarify what is being asked and what a complete answer contains.
- State your assumptions explicitly before working the problem.
- Say what you would check first and why it is the highest-information step.
- Work from the requirement backwards to the design.
Follow-up
- What assumption would you test first?
- How would you know your answer was wrong?
If given a project with a tight deadline, how would you ensure its success?
If given a project with a tight deadline, how would you ensure its success?
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 would you use to gather requirements from stakeholders?
What strategies would you use to gather requirements from stakeholders?
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 approach debugging an application?
How do you approach debugging an 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 Charles River Laboratories candidates report.
Prepare, practise & reflect
One practical outcome each day. Spend longer where you need it.
0 / 7 done01Map the Charles River Laboratories loop
- Write out the reported sequence: Phone Screen, Technical 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 2 reported rounds, with the weakest marked.
02Work Programmable Logic Control (PLC)
- Spend the session on Programmable Logic Control (PLC), which Charles River Laboratories candidates report being tested on.
- Write one worked example in Programmable Logic Control (PLC) and time yourself on it.
Deliverable: One timed worked example in Programmable Logic Control (PLC).
03Work SQL
- Spend the session on SQL, which Charles River Laboratories candidates report being tested on.
- Write one worked example in SQL and time yourself on it.
Deliverable: One timed worked example in SQL.
04Work C#
- Spend the session on C#, which Charles River Laboratories 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: What programming languages are you most proficient in, and why?
- Answer aloud, timed: Can you explain the concept of object-oriented programming?
Deliverable: Spoken answers to 2 reported Technical / Domain Questions question(s), under time.
06Answer out loud: Behavioral / Leadership Questions
- Answer aloud, timed: Describe a time when you had to work under pressure. How did you handle it?
- Answer aloud, timed: Can you give an example of how you resolved a conflict within a team?
Deliverable: Spoken answers to 2 reported Behavioral / Leadership Questions question(s), under time.
07Answer out loud: Problem-Solving / Case Studies
- Answer aloud, timed: How would you approach designing a software system for managing laboratory data?
- Answer aloud, timed: If given a project with a tight deadline, how would you ensure its success?
Deliverable: Spoken answers to 2 reported Problem-Solving / Case Studies 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 when you had to work under pressure. How did you handle it?
Describe a time when you had to work under pressure. 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?
Can you give an example of how you resolved a conflict within a team?
Can you give an example of how you resolved a 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?
What motivates you to succeed in your role?
What motivates you to succeed 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 your tasks when managing multiple projects?
How do you prioritize your tasks when managing 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?
Describe a situation where you had to learn a new technology quickly.
Describe a situation where you had to learn a new technology quickly.
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 make a significant decision based on data analysis.
Describe a time when you had to make a significant decision based on data analysis.
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 exceptions in your code?
How do you handle exceptions in your code?
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 when you had to work under pressure. How did you handle it?
- 02
Can you give an example of how you resolved a conflict within a team?
- 03
What motivates you to succeed in your role?
- 04
How do you prioritize your tasks when managing multiple projects?
How difficult is the interview process, and how much preparation time should I expect?
The interview process can be challenging, especially for technical roles. Candidates typically spend several weeks preparing, focusing on both technical skills and behavioral responses.
Charles River Laboratories Software Engineer candidate reports ↗What differentiates successful candidates at Charles River Laboratories?
Successful candidates demonstrate strong technical capabilities, effective problem-solving skills, and a solid cultural fit with the company’s values of collaboration and integrity.
Charles River Laboratories Software Engineer candidate reports ↗What is the company culture like?
Charles River Laboratories fosters a collaborative and innovative culture that values teamwork and open communication. Employees are encouraged to contribute ideas and take initiative in their roles.
Charles River Laboratories Software Engineer candidate reports ↗What is the typical timeline from initial screen to offer?
The timeline varies but generally ranges from a few weeks to a couple of months, depending on scheduling and the number of interview rounds.
Charles River Laboratories Software Engineer candidate reports ↗Are there remote work options or hybrid expectations?
Charles River Laboratories is open to flexible working arrangements, including remote work and hybrid models, depending on the role and department.
Charles River Laboratories Software Engineer candidate reports ↗What topics does Charles River Laboratories test in interviews?
Charles River Laboratories interviews most often cover SQL, Stakeholder Communication, Cross-Functional Collaboration, Requirements Gathering, and Behavioral Interviewing. The exact emphasis depends on the specific role you apply for.
Charles River Laboratories 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.
- 01Charles River Laboratories 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
Explore related engineering environments and compare the preparation focus.
Cognition Software Engineer Interview Guide
What Cognition asks Software Engineer candidates, from reported rounds and questions.
Vercel Software Engineer Interview Guide
Debugging practice for Vercel software engineer prep built on a reproduction you trust, narrowing to the smallest failing input, and changing one variable per run so the result stays attributable.
Together Ai Software Engineer Interview Guide
Failure-handling practice for Together Ai software engineer candidates: requests whose outcome a timeout leaves unknown, where a retry is safe, and deduplicating at the receiver instead of assuming exactly-once delivery.
Spotify Software Engineer Interview Guide
Timed practice for Spotify software engineer candidates who lose time to the clock: short problems taken end to end, then reviewed against a written rubric rather than a passing test run.