As a Software Engineer at CMR Surgical, you are at the intersection of cutting-edge robotics and life-saving medical technology. You will be instrumental in developing the software that powers the Versius Surgical Robotic System, ensuring that surgeons can perform complex procedures with unprecedented precision and control. This role is not merely about writing code; it is about building reliable, high-performance systems that function in critical, real-time environments. You will join a multidisciplinary team of engineers, scientists, and clinicians to solve complex challenges in motion control, system integration, and user interface design. Your work will directly influence the safety and efficacy of surgical robotics, requiring a rigorous approach to software development, testing, and documentation. If you are driven by the challenge of solving high-stakes engineering problems where precision is paramount, this role offers a unique opportunity to shape the future of digital surgery. ##### Tip Your work at CMR Surgical will be subject to strict regulatory standards. Familiarize yourself with the importance of software safety and traceability in medical devices.
Initial Screening
reportedThe process begins with an initial screening to assess basic qualifications and fit.
What to demonstrate
- The process begins with an initial screening to assess basic qualifications and fit
- Depth in Robotics Software Engineering
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 Dives
reportedCandidates undergo deeper technical interviews to evaluate their problem-solving skills.
What to demonstrate
- Candidates undergo deeper technical interviews to evaluate their problem-solving skills
- Depth in Robotics Software Engineering
How to prepare
- Answer aloud and timed: How do you balance the need for rapid development with the requirements of a safety-critical product?
- Answer aloud and timed: What strategies do you use for unit testing and integration testing in a robotics environment?
Final Round
reportedCandidates meet the wider team to assess cultural alignment and collaborative atmosphere.
What to demonstrate
- Candidates meet the wider team to assess cultural alignment and collaborative atmosphere
- Depth in Robotics Software Engineering
How to prepare
- Answer aloud and timed: How do you handle resource constraints (memory, CPU) when designing software for hardware platforms?
- Answer aloud and timed: Describe a time you had to optimize a piece of code that was causing system latency.
PracHub editorial advice for the preparation topics above.
Prepare for the "Why
Don't just explain how you solved a problem; be ready to explain why you chose that specific approach over others.
Embrace the Safety Mindset
Always consider failure states and safety protocols in your technical answers.
Be Collaborative
When solving problems during the interview, think out loud. We want to see how you think and how you respond to feedback.
Know the Product
Research the Versius Surgical Robotic System to understand the specific engineering challenges we face.
Choose a category, try a prompt, then open its approach, worked solution or follow-up when you need it.
How do you ensure real-time performance in a multi-threaded application?
How do you ensure real-time performance in a multi-threaded application?
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?
Track a rolling failure rate per destination for circuit decisions
The egress service delivers about 1,500 webhooks per second across roughly 40,000 destinations, each call bounded by a 10 second timeout. Maintain, per destination, the failure rate over the trailing 60 seconds so a caller can ask before dispatch whether the circuit should open. Attempts arrive as (destination_id, finished_at_ms, outcome). Requirement: amortised O(1) per attempt, with total memory bounded by the destination count rather than by traffic. Give the structure, its exact memory, and the rule that stops a destination with three attempts from opening a circuit.
Approach
- Name the exact-deque version and then reject it as the default. Holding timestamps and advancing a tail pointer past anything older than now minus 60 seconds is a correct two-pointer window at amortised O(1) per attempt, but its memory tracks in-window traffic, so one destination in a retry storm holds hundreds of thousands of entries while thousands of quiet destinations hold none.
- Use a ring of 60 one-second buckets per destination, each bucket a pair of counters for attempts and failures. On an attempt, advance the ring by the elapsed whole seconds, zeroing at most min(elapsed, 60) buckets, then increment the head. That is amortised O(1) with a fixed footprint per destination.
- State the footprint: 60 buckets times two 4-byte counters is 480 bytes of payload per destination, so 40,000 destinations is roughly 20 to 25 MB with per-entry overhead, bounded by the catalogue rather than by the rate. The cost is granularity, since the oldest bucket ages out in whole seconds, which is far tighter than the decision needs.
- Require a minimum sample before the circuit may open. A destination with three attempts and three failures reads as 100 percent and is not evidence; a floor of roughly 20 attempts in the window makes the ratio meaningful, and below that floor use a run of consecutive failures as the trigger instead.
Follow-up
- The fleet is 30 instances and each sees roughly a thirtieth of a destination's traffic. Where does the rate actually live, and what does a per-instance answer get wrong?
- A destination answers in 9.5 seconds and succeeds. It is not failing but it is consuming your per-destination concurrency. What signal should open the circuit here?
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?
Find version gaps and relay lag with window functions
outbox_event holds event_id, aggregate_type, aggregate_id, aggregate_version, event_type, payload, status ('pending','published','dead'), attempts, created_at, published_at. A projection is missing rows and you must decide whether the relay skipped events or the consumer dropped them. Write three queries over the last seven days: one listing every aggregate_id whose published aggregate_version sequence has a hole, one giving per-day counts with a running total, and one returning the newest published event per aggregate. For each, say where the window function is evaluated relative to WHERE and LIMIT. PostgreSQL 16.
Approach
- Gaps: compute lead(aggregate_version) OVER (PARTITION BY aggregate_id ORDER BY aggregate_version) in a subquery, then filter next_version <> aggregate_version + 1 in the outer query. Window functions are evaluated after WHERE, GROUP BY and HAVING and before the outer ORDER BY and LIMIT, so the predicate cannot sit in the same WHERE clause and PostgreSQL 16 has no QUALIFY.
- Say what the seven-day filter does to the answer: it truncates every partition, so the first row per aggregate has no predecessor inside the window and a hole spanning the boundary is invisible. Widen the window, or join to resource.version as the authority for the true maximum.
- Running total: SELECT date_trunc('day', created_at) AS d, count() AS n, sum(count()) OVER (ORDER BY date_trunc('day', created_at) ROWS UNBOUNDED PRECEDING). An aggregate inside a window call is legal because grouping runs before windowing. The grouping key is unique per row here so ROWS and RANGE agree, but write the frame anyway — over ungrouped rows with tied timestamps the default RANGE frame pulls in every peer row and the total jumps.
- Newest per aggregate: DISTINCT ON (aggregate_id) ... ORDER BY aggregate_id, aggregate_version DESC is the cheap PostgreSQL-only form when an index matches that order; row_number() OVER (PARTITION BY aggregate_id ORDER BY aggregate_version DESC) = 1 is the portable form and needs a subquery for the same evaluation-order reason as the gap query.
Follow-up
- Relay failover redelivers events. Does a duplicate break the gap query, and how would you detect one from this table alone?
- Turn the gap check into a continuous monitor rather than a query someone runs after an incident. What does it watch?
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?
How do you balance the need for rapid development with the requirements of a safety-critical product?
How do you balance the need for rapid development with the requirements of a safety-critical product?
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 unit testing and integration testing in a robotics environment?
What strategies do you use for unit testing and integration testing in a robotics environment?
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?
How would you design a communication protocol between a robotic arm and a control console?
How would you design a communication protocol between a robotic arm and a control console?
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 steps do you take to ensure software modularity when working on a large-scale robotics project?
What steps do you take to ensure software modularity when working on a large-scale robotics project?
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?
Can you explain your approach to debugging intermittent issues in embedded systems?
Can you explain your approach to debugging intermittent issues in embedded systems?
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 CMR Surgical candidates report.
Prepare, practise & reflect
One practical outcome each day. Spend longer where you need it.
0 / 7 done01Map the CMR Surgical loop
- Write out the reported sequence: Initial Screening, Technical Dives, Final Round.
- 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 Robotics Software Engineering
- Spend the session on Robotics Software Engineering, which CMR Surgical candidates report being tested on.
- Write one worked example in Robotics Software Engineering and time yourself on it.
Deliverable: One timed worked example in Robotics Software Engineering.
03Work Hardware-Software Integration
- Spend the session on Hardware-Software Integration, which CMR Surgical candidates report being tested on.
- Write one worked example in Hardware-Software Integration and time yourself on it.
Deliverable: One timed worked example in Hardware-Software Integration.
04Work Embedded Systems
- Spend the session on Embedded Systems, which CMR Surgical candidates report being tested on.
- Write one worked example in Embedded Systems and time yourself on it.
Deliverable: One timed worked example in Embedded Systems.
05Answer out loud: Technical and Domain Expertise
- Answer aloud, timed: How do you ensure real-time performance in a multi-threaded application?
- Answer aloud, timed: Can you explain your approach to debugging intermittent issues in embedded systems?
Deliverable: Spoken answers to 2 reported Technical and Domain Expertise question(s), under time.
06Answer out loud: Problem Solving and Architecture
- Answer aloud, timed: Describe a time you had to optimize a piece of code that was causing system latency.
- Answer aloud, timed: How would you design a communication protocol between a robotic arm and a control console?
Deliverable: Spoken answers to 2 reported Problem Solving and Architecture question(s), under time.
07Dry run for CMR Surgical
- Run one full mock under time, then write down the two questions you most want to ask your interviewers.
Deliverable: A completed timed mock and two questions to ask.
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 resource constraints (memory, CPU) when designing software for hardware platforms?
How do you handle resource constraints (memory, CPU) when designing software for hardware platforms?
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 you had to optimize a piece of code that was causing system latency.
Describe a time you had to optimize a piece of code that was causing system latency.
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 failure states in a system where downtime is not an option?
How do you handle failure states in a system where downtime is not an option?
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 resource constraints (memory, CPU) when designing software for hardware platforms?
- 02
Describe a time you had to optimize a piece of code that was causing system latency.
- 03
How do you handle failure states in a system where downtime is not an option?
How long does the interview process typically take?
The process varies by candidate and team, but generally spans several weeks to ensure we have enough time to thoroughly evaluate technical depth and cultural fit.
CMR Surgical Software Engineer candidate reports ↗Is there a coding test?
Yes, expect technical assessments that may include live coding or take-home exercises designed to test your ability to write clean, efficient, and safe code.
CMR Surgical Software Engineer candidate reports ↗What is the company culture like?
CMR Surgical is mission-driven and collaborative. We value curiosity, technical rigor, and the ability to work in a fast-paced environment where safety is the top priority.
CMR Surgical Software Engineer candidate reports ↗Can I work remotely?
Our engineering teams are largely based in Cambridge, England, to facilitate close collaboration with the physical robotic hardware. Most roles require an on-site presence.
CMR Surgical Software Engineer candidate reports ↗What topics does CMR Surgical test in interviews?
CMR Surgical interviews most often cover Project Management, Robotics Software Engineering, Workflow Analysis, Managing Competing Priorities, and Hardware-Software Integration. The exact emphasis depends on the specific role you apply for.
CMR Surgical 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.
- 01CMR Surgical 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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