As a Software Engineer at Merck, you play a vital role in building and scaling technology solutions that directly support global healthcare innovations, pharmaceutical research, and life-saving manufacturing operations. Your code and system architecture help drive critical data pipelines, automation workflows, and internal enterprise platforms that empower scientists, engineers, and clinical teams to deliver therapeutics to patients faster. Whether you are developing cloud-native microservices, integrating IoT infrastructure, or optimizing backend data processing, your work bridges the gap between cutting-edge computer science and modern pharmaceutical manufacturing. This position sits at the intersection of high-availability software engineering and heavily regulated scientific environments. You will tackle complex technical challenges involving secure cloud environments (such as AWS), containerization tools like Docker and Kubernetes, and enterprise frameworks like Java Spring Boot or Node.js. Because operates at a massive global scale, systems reliability, data integrity, and strict adherence to process engineering standards are paramount. You will frequently collaborate with cross-functional teams spanning data science, infrastructure, validation, and product management to deliver robust, maintainable software. Merck Expect a collaborative yet rigorous engineering culture where technical depth must be paired with clear communication and a deep respect for compliance.
Phone Screening
reportedInitial call to assess candidate's background and fit for the role.
What to demonstrate
- Initial call to assess candidate's background and fit for the role
- Depth in Data Structures & Algorithms
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 Assessments
reportedEvaluation of technical proficiency through coding challenges or tests.
What to demonstrate
- Evaluation of technical proficiency through coding challenges or tests
- Depth in Data Structures & Algorithms
How to prepare
- Answer aloud and timed: How do you implement data structures and sorting algorithms efficiently when handling large datasets?
- Answer aloud and timed: What is your experience with AWS services, and how do you utilize libraries like boto3 for cloud automation?
Behavioral Interviews
reportedInterviews focused on assessing cultural fit and alignment with company values.
What to demonstrate
- Interviews focused on assessing cultural fit and alignment with company values
- Depth in Data Structures & Algorithms
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 interviews above and write down what you would ask to confirm before it.
Team Discussions
reportedConversations with potential team members to evaluate collaboration and fit.
What to demonstrate
- Conversations with potential team members to evaluate collaboration and fit
- Depth in Data Structures & Algorithms
How to prepare
- Answer aloud and timed: What is your familiarity with database management, service cataloging, and platforms like ServiceNow and CMDB?
- Answer aloud and timed: If you are interviewing for specialized or manufacturing-adjacent roles, how do you approach SAS programming or clinical data standards like SDTM and ADAM?
Final Assessments
reportedComprehensive evaluation to finalize candidate suitability for the role.
What to demonstrate
- Comprehensive evaluation to finalize candidate suitability for the role
- Depth in Data Structures & Algorithms
How to prepare
- Answer aloud and timed: How do you design systems that maintain high availability and data integrity under strict regulatory constraints?
- Answer aloud and timed: Can you walk through a specific project on your resume and explain the technical challenges you overcame?
1 candidate reports. Individual accounts describe a particular role and hiring cycle.
Merck Software Engineer interview: long final campus day
After I applied online, the early response was quick: an HR phone screen followed by a video interview with the hiring manager. I was then invited to a final-round onsite at the Rahway campus for top candidates. That day included about 6 to 7 interviews and a 45-minute presentation. The manager conversation came roughly 5 to 6 weeks before the onsite, and it took several more weeks to hear back.…
Read full experiencePracHub editorial advice for the preparation topics above.
Master the STAR method for behavioral questions
Expect a high volume of competency-based questions exploring your past experiences. Frame your answers by clearly stating the Situation, Task, Action, and Result, making sure to highlight your specific individual contributions.
Communicate your thought process out loud
During live coding and system design rounds, interviewers care as much about how you think as they do about your final answer. Talk through your assumptions, acknowledge edge cases, and treat the interviewer as a collaborative partner.
Brush up on core computer science fundamentals
Do not neglect basic sorting algorithms, data structures, and object-oriented design principles. Even in enterprise settings, initial technical screens frequently validate these core competencies.
Connect your work to the broader mission
Whenever possible, ground your technical examples in how they drive operational reliability or business value. Showing an awareness of the end user and organizational context sets top candidates apart.
Choose a category, try a prompt, then open its approach, worked solution or follow-up when you need it.
Can you explain how closures work in backend development and provide an example in Node.js?
Can you explain how closures work in backend development and provide an example in Node.js?
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?
How do you implement data structures and sorting algorithms efficiently when handling large datasets?
How do you implement data structures and sorting algorithms efficiently when handling large datasets?
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?
Diff a projection against the primary without per-row point reads
The listing projection has drifted and some rows show a stale version. The primary holds 40,000,000 resource rows across 12,000 tenants while serving 1,200 writes and 14,000 reads per second. The obvious repair, reading each resource row and comparing its version against the projection, is correct and would eventually finish. Explain precisely why it is unacceptable here, then give a diff that finds the differing rows, state its complexity, and make it safe to run against a live primary. Replication lag is usually under 100 ms and is not bounded.
Approach
- Quantify the naive cost rather than calling it slow: 40,000,000 point reads at even 0.5 ms each is over five hours serialised, and the only lever is concurrency, which is exactly what you cannot spend. The primary's pool is sized for the write path, and 40,000,000 random reads evict the buffer cache that sustains the 85 percent cache hit rate, so the audit degrades the system it is auditing.
- Replace random access with one ordered pass per side. Both sides can be read in (tenant_id, resource_id) order, which is a sequential scan on each and a merge join in O(n) time and O(1) memory. For a dense diff that is the whole answer, and it reads the primary once instead of 40,000,000 times.
- For the expected sparse case, compare range hashes instead of rows: partition the key space, compute per range an order-independent aggregate over hash(resource_id, version), compare aggregates, and descend only into ranges that differ. With d differing rows and branching factor B, at most d ranges mismatch per level, so the drill-down examines O(d log_B(n/d)) ranges and reads full rows only in mismatching leaves.
- Aggregate with a sum modulo 2^64 or a multiset hash, never XOR. XOR is order-independent but self-cancelling, so two rows wrong in the same way, or a row duplicated on one side, leave the range aggregate matching and the range is declared clean.
Follow-up
- The diff reports 900 stale rows. How do you decide between patching those rows and rebuilding the projection from resource_revision?
- Same job, but the projection lives in a search index that cannot be scanned in key order. What changes?
Hold a per-tenant active cap against concurrent creates
A tenant on the standard plan may hold at most 50 resources with status='active'. The create handler runs SELECT count(*) FROM resource WHERE tenant_id = $1 AND status = 'active', compares to 50, then inserts. Two creates arrive 3 ms apart on different instances and the tenant lands at 51. Name the anomaly, say whether PostgreSQL 16 READ COMMITTED or REPEATABLE READ prevents it and why, then give an implementation that holds the cap at READ COMMITTED with the exact statements. Finally, say what changes when the cap is 'at most one running export per tenant' on job_run.
Approach
- Name it: write skew. The two transactions read an overlapping set and write disjoint rows, so there is no row-level conflict for the engine to detect and each commit is individually legal.
- Rule out the levels precisely. READ COMMITTED takes a fresh snapshot per statement and takes no lock on the counted rows, so both see 49. PostgreSQL's REPEATABLE READ is snapshot isolation: it removes non-repeatable reads and phantoms within the snapshot but still admits write skew, because the anomaly is not a re-read of a changed row, it is a read of a set that a concurrent transaction invalidates. Only SERIALIZABLE closes it, by tracking the read dependency and aborting one transaction with SQLSTATE 40001 — a guarantee that exists only if the application re-runs the whole transaction from the read.
- Convert the set predicate into a single-row conflict: keep tenant.active_resource_count and run UPDATE tenant SET active_resource_count = active_resource_count + 1 WHERE tenant_id = $1 AND active_resource_count < 50 in the same transaction as the INSERT. Zero affected rows is the cap, returned as 409. The row lock serialises the decision at any isolation level, and contention is bounded to one tenant's row — which is also the fair-scheduling unit, unlike a global counter that would convoy every tenant behind one row.
- State the cost you just took on: a counter is a second source of truth that can drift, so every path that changes status must adjust it inside the same transaction, and a periodic reconciliation has to exist, with resource_revision as the authority for what the count should have been.
Follow-up
- A resource moves from archived back to active. Which statements change, and what breaks if the counter update and the status change land in different transactions?
- The cap becomes plan-dependent and a plan can change mid-month. Where does the number 50 live, and who reads it?
Write the update path that detects a concurrent edit
resource carries version INT NOT NULL DEFAULT 1. resource_revision holds revision_id, resource_id, version, actor_user_id, change_kind, patch JSONB, request_id, created_at with UNIQUE (resource_id, version). outbox_event holds aggregate_type, aggregate_id, aggregate_version, event_type, payload, status. A PUT carries the version the client read. Write the exact statements for the single transaction that applies the edit, records the revision and enqueues 'resource.updated', and give the handler's branch on zero affected rows. Then say what PostgreSQL 16 does under READ COMMITTED when two of these updates hit one row at once.
Approach
- One transaction, three writes, no network call inside it: UPDATE resource SET title = $3, version = version + 1, updated_at = now() WHERE resource_id = $1 AND tenant_id = $4 AND version = $2; then INSERT the resource_revision row at version $2 + 1; then INSERT the outbox_event row at the same aggregate_version. The event goes to a table rather than a broker because no transaction spans both.
- Branch on the affected-row count before doing anything else. Zero has three causes — stale version, wrong tenant, row gone — so re-read once and map to 409 carrying the current version, or 404 for an id outside the caller's tenant, which also stops the endpoint confirming that another tenant's id exists.
- State the engine behaviour instead of assuming it. Under READ COMMITTED the second UPDATE blocks on the row lock, and when the first commits PostgreSQL re-evaluates the WHERE clause against the newly committed row, so the version predicate now fails and the statement reports zero rows. Under REPEATABLE READ the identical collision raises SQLSTATE 40001 instead, so the handler must fold both shapes into one conflict response.
- Keep UNIQUE (resource_id, version) even though the predicate already serialises writers. It is what makes a lost update unwritable if any other path ever reaches the revision table, and it converts a logic bug into 23505 rather than into a silently missing history row.
Follow-up
- A client sends the version it read ten minutes ago and the resource has moved three versions. What is in your 409 so it can resolve the conflict without a full re-fetch?
- Two editors, two disjoint fields, no overlap. Does your answer still refuse the second write, and should it?
What are the core principles of object-oriented design, and how do you apply SOLID principles in your daily co
What are the core principles of object-oriented design, and how do you apply SOLID principles in your daily coding?
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 walk through your experience with Java, Spring Boot, and building scalable microservices architectures
Can you walk through your experience with Java, Spring Boot, and building scalable microservices architectures?
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 do you approach containerization and orchestration using Docker and Kubernetes?
How do you approach containerization and orchestration using Docker and Kubernetes?
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 is your familiarity with database management, service cataloging, and platforms like ServiceNow and CMDB?
What is your familiarity with database management, service cataloging, and platforms like ServiceNow and CMDB?
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?
If you are interviewing for specialized or manufacturing-adjacent roles, how do you approach SAS programming o
If you are interviewing for specialized or manufacturing-adjacent roles, how do you approach SAS programming or clinical data standards like SDTM and ADAM?
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 do you design systems that maintain high availability and data integrity under strict regulatory constrain
How do you design systems that maintain high availability and data integrity under strict regulatory constraints?
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?
Edge instances grow 400 MB per hour until the nightly restart
Edge API instances start at 700 MB resident and grow about 400 MB/hour; a nightly rolling restart has hidden it for weeks. Growth continues unchanged when request rate halves overnight, p99 degrades in the last hours before an instance is recycled, and heap used immediately after a forced full GC rises monotonically. The service holds no product state. Name the discriminating measurement that separates the plausible causes, give the most likely cause, and give the fix and how you would verify it.
Approach
- Separate resident memory from live heap first, because they fail differently. Resident size can grow from fragmentation, native buffers or thread stacks while the heap is flat; heap used after a full GC rising monotonically is the measurement that says objects are reachable and not being released. You already have it, so this is retention, not fragmentation, and that closes off half the candidate list.
- Use the rate's independence from traffic as the discriminator. Growth that continues at half the request rate rules out per-request objects that are merely slow to collect and points at a structure that grows with distinct values observed rather than with call volume. Write the candidates that have that property: a metrics registry keyed on a high-cardinality label, an unevicted cache, an interner, a per-key lock map.
- Take two heap snapshots an hour apart and diff by retained size, reading the dominator tree, not by allocation count or instance count. Expect one root holding a map with millions of entries, then follow the reference chain to the code that inserts and never removes. Allocation profilers point at churn, which is the wrong signal here.
- The candidate that fits this service is an observability label carrying an identifier, such as a request path recorded before templating so that /v1/resources/48213 becomes its own metric series. That grows with distinct ids seen, is independent of rate, and explains the late p99 degradation, since GC cost rises with the size of the live set.
Follow-up
- Post-GC heap is now flat but resident size still creeps. What are you looking at, and does it matter?
- How would you have detected this before an OOM, given the nightly restart masked the trend?
Built from the rounds and topics Merck candidates report.
Prepare, practise & reflect
One practical outcome each day. Spend longer where you need it.
0 / 7 done01Map the Merck loop
- Write out the reported sequence: Phone Screening, Technical Assessments, Behavioral Interviews, Team Discussions, Final Assessments.
- 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 Data Structures & Algorithms
- Spend the session on Data Structures & Algorithms, which Merck candidates report being tested on.
- Write one worked example in Data Structures & Algorithms and time yourself on it.
Deliverable: One timed worked example in Data Structures & Algorithms.
03Work SAS Programming
- Spend the session on SAS Programming, which Merck candidates report being tested on.
- Write one worked example in SAS Programming and time yourself on it.
Deliverable: One timed worked example in SAS Programming.
04Work Drug Development Domain Knowledge
- Spend the session on Drug Development Domain Knowledge, which Merck candidates report being tested on.
- Write one worked example in Drug Development Domain Knowledge and time yourself on it.
Deliverable: One timed worked example in Drug Development Domain Knowledge.
05Answer out loud: Technical and Domain Expertise
- Answer aloud, timed: Can you explain how closures work in backend development and provide an example in Node.js?
- Answer aloud, timed: What are the core principles of object-oriented design, and how do you apply SOLID principles in your daily coding?
Deliverable: Spoken answers to 2 reported Technical and Domain Expertise question(s), under time.
06Answer out loud: System Architecture and Domain-Specific Tools
- Answer aloud, timed: How do you approach containerization and orchestration using Docker and Kubernetes?
- Answer aloud, timed: What is your familiarity with database management, service cataloging, and platforms like ServiceNow and CMDB?
Deliverable: Spoken answers to 2 reported System Architecture and Domain-Specific Tools question(s), under time.
07Answer out loud: Behavioral and Experience Deep Dives
- Answer aloud, timed: Can you walk through a specific project on your resume and explain the technical challenges you overcame?
- Answer aloud, timed: Tell me about a time when you had to improve an existing software or operational process. What steps did you take?
Deliverable: Spoken answers to 2 reported Behavioral and Experience Deep Dives 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.
What is your experience with AWS services, and how do you utilize libraries like boto3 for cloud automation?
What is your experience with AWS services, and how do you utilize libraries like boto3 for cloud automation?
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 walk through a specific project on your resume and explain the technical challenges you overcame?
Can you walk through a specific project on your resume and explain the technical challenges you overcame?
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 when you had to improve an existing software or operational process. What steps did you t
Tell me about a time when you had to improve an existing software or operational process. What steps did you take?
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 navigated an interpersonal dispute or a disagreement within a multidisciplinary
Describe a situation where you navigated an interpersonal dispute or a disagreement within a multidisciplinary 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 is your greatest professional strength, and what is a key lesson you learned from a past failure?
What is your greatest professional strength, and what is a key lesson you learned from a past failure?
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 approach cross-functional collaboration when working alongside non-technical stakeholders or domain
How do you approach cross-functional collaboration when working alongside non-technical stakeholders or domain experts?
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
What is your experience with AWS services, and how do you utilize libraries like boto3 for cloud automation?
- 02
Can you walk through a specific project on your resume and explain the technical challenges you overcame?
- 03
Tell me about a time when you had to improve an existing software or operational process. What steps did you take?
- 04
Describe a situation where you navigated an interpersonal dispute or a disagreement within a multidisciplinary team.
How difficult is the interview process, and how much preparation time should I plan for?
The interview process is moderately rigorous, combining algorithmic coding checks, system design evaluations, and structured behavioral panels. Most candidates benefit from dedicating 4 to 6 weeks of focused preparation, refreshing their data structures, practicing system architecture problems, and reviewing their past projects through the STAR method.
Merck Software Engineer candidate reports ↗What is the company culture like for engineering teams at Merck?
The culture is collaborative, professional, and mission-driven. Teams value work-life balance while maintaining a strong commitment to scientific excellence and regulatory compliance. Engineers operate in an environment where mentorship and cross-functional teamwork are actively encouraged.
Merck Software Engineer candidate reports ↗How long does the entire interview process take from application to final decision?
The timeline can vary significantly depending on the hiring hub and team needs. While some initial screenings move quickly, subsequent rounds—including technical panels, manager interviews, and potential onsite loops—can stretch across several weeks, so patience and proactive communication are key.
Merck Software Engineer candidate reports ↗Are hybrid or remote work options available for this role?
Many software engineering positions at Merck operate under a hybrid model, typically requiring a set number of days per week in regional hubs such as West Point, Pennsylvania or Rahway, New Jersey. Be sure to verify the specific location and attendance policy with your recruiter during the initial screening.
Merck Software Engineer candidate reports ↗What topics does Merck test in interviews?
Merck interviews most often cover Data Analysis, Behavioral Interviewing, Problem Solving, SQL, and Python. The exact emphasis depends on the specific role you apply for.
Merck 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.
- 01Merck 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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