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Komline-Sanderson Software Engineer Interview Guide

Komline-Sanderson Software Engineer interview guide: reported rounds, questions and how candidates describe the process.

The 60-second brief

At Komline-Sanderson, a Software Engineer plays a unique and highly interdisciplinary role that bridges the gap between digital systems and heavy industrial machinery. Unlike traditional software roles focused solely on web applications or SaaS products, engineering at Komline-Sanderson directly impacts physical, real-world infrastructure. You will design, develop, and optimize the control systems, automation software, and network architectures that power world-class filtration, environmental, and waste-processing equipment. Your work will directly influence the safety, efficiency, and reliability of systems deployed in municipal wastewater plants, chemical processing facilities, and manufacturing environments globally. This means writing code and configuring systems where performance and safety are paramount.

This guide is scoped to a Software Engineer candidate at Komline-Sanderson.

Focus areas

  • CNC Programming (Computer Numerical Control)
  • Network Engineering
  • Applications Engineering

The Komline-Sanderson interview process

Komline-Sanderson candidates report 3 rounds over 3-5 weeks. The stages below are what candidates describe, not a published process.

Initial Alignment

The process begins with an initial alignment to assess mutual fit between the candidate and the company.

What to demonstrate

  • The process begins with an initial alignment to assess mutual fit between the candidate and the company
  • Depth in CNC Programming (Computer Numerical Control)

How to prepare

  • Answer aloud and timed: Explain how you would structure a PLC program to handle an emergency stop condition safely.
  • Answer aloud and timed: Describe your experience with G-code and M-code optimization for CNC machinery.

Deep Technical Evaluations

Candidates undergo in-depth technical evaluations focusing on practical skills and real-world scenarios.

What to demonstrate

  • Candidates undergo in-depth technical evaluations focusing on practical skills and real-world scenarios
  • Depth in CNC Programming (Computer Numerical Control)

How to prepare

  • Answer aloud and timed: How do you handle signal noise or latency when reading analog sensor data in a control loop?
  • Answer aloud and timed: Walk us through your process for designing a human-machine interface (HMI) that is intuitive for plant operators.

Panel and Onsite Stages

Candidates participate in panel discussions and onsite evaluations to further assess technical capabilities and team dynamics.

What to demonstrate

  • Candidates participate in panel discussions and onsite evaluations to further assess technical capabilities and team dynamics
  • Depth in CNC Programming (Computer Numerical Control)

How to prepare

  • Answer aloud and timed: What strategies do you use to debug a synchronization issue between multiple servo drives?
  • Answer aloud and timed: How would you design a redundant network topology for a manufacturing facility to ensure zero downtime?

Where candidates lose points

Connect code to hardware

Whenever you describe a software solution or programming project, always explain how it impacted the physical system. Mention the sensors, motors, safety limits, or operator interfaces that your software interacted with.

Highlight your troubleshooting methodology

Interviewers value a structured approach to solving problems. Use the STAR method (Situation, Task, Action, Result) to explain how you diagnosed a complex failure, emphasizing how you isolated variables and verified your solution.

Brush up on industrial standards

Be ready to discuss relevant industry codes and standards (such as National Electrical Code (NEC), UL 508A for industrial control panels, or ISA-95 for enterprise-control system integration) if applicable to your track.

Questions & practice

Tell us about a project where the initial specifications were highly ambiguous. How did you define the require

Medium · Behavioral & Project Management

Tell us about a project where the initial specifications were highly ambiguous. How did you define the requirements and deliver the solution?

Approach

  1. Restate the input: its shape, its size, and what is guaranteed about it.
  2. Name the brute-force solution and its complexity before improving on it.
  3. Choose the data structure from the access pattern, not from familiarity.
  4. 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?

Find overlapping job attempts and peak concurrency from lease records

Medium · sweep line · intervals · leases

A day of job_run history yields about 50,000,000 attempt records: (job_run_id, job_type, attempt, started_at, finished_at which is NULL when the worker died, lease_expires_at). Leases expire on a clock, so a job that outran its lease ran twice. Produce (a) every job_run_id whose attempts overlapped in wall-clock time and (b) the peak number of simultaneously running attempts per job_type with the minute it occurred. Target O(n log n). State how you treat a NULL finished_at and what clock skew does to your answer.

Approach

  1. Define the interval before sorting anything: an attempt occupies [started_at, COALESCE(finished_at, lease_expires_at)). finished_at is observed and lease_expires_at is only a promise, so every attempt without a finish contributes an estimate and the whole result is a lower bound on overlap rather than an exact count.
  2. For peak concurrency, sweep: emit 2n endpoints, sort by (timestamp, kind) with ends ordered before starts at equal timestamps, then walk the sequence maintaining a counter per job_type and record each type's maximum with its timestamp. O(n log n) dominated by the sort, O(n) space, or O(1) extra if the sort is external and the walk streams.
  3. For overlap detection, do not compare attempts pairwise. A single global sort by (job_run_id, started_at) gives both the grouping and the order; within a group, keep the maximum end seen so far and report an overlap exactly when the next start is less than that running maximum, which is one linear pass after the sort.
  4. Half-open intervals matter and are easy to get wrong: with closed intervals an attempt ending at the same millisecond another begins reads as concurrency two, and across 50,000,000 records that artefact swamps the real signal.

Follow-up

  • A handler is not idempotent and you have found 400 overlapping jobs. Which of them actually caused damage, and what would you query to find out?
  • Peak concurrency for one job_type is 4 against a configured cap of 4. Is the cap working, or is the data hiding attempts that never started?

Collapse a redelivered event batch into per-aggregate high-water marks

Easy · hashing · at-least-once · aggregation

You drain a batch of up to 5,000,000 events, each (aggregate_id BIGINT, aggregate_version INT, event_type, payload). The log guarantees order within one aggregate only; the batch merges 64 partitions, and a relay failover has redelivered a range, so an older version for an aggregate can appear after a newer one. Given a map of last_applied_version per aggregate, produce the events worth applying, at most one per (aggregate_id, version), plus the count discarded. Target O(n) time. State the memory for 2,000,000 distinct aggregates and what you do when it does not fit.

Approach

  1. One pass, one hash map from aggregate_id to the highest version kept, and a discard counter. An event whose version is at or below last_applied_version for its aggregate is dropped without further work, which is the whole reason the event carries its version rather than a delta. O(n) expected time, O(d) space in distinct aggregates.
  2. Keep the maximum, never the last occurrence. The redelivered range means the final appearance of an aggregate in the batch can be an older version than one seen earlier in the same batch, so last-wins applies stale state over newer state and the projection regresses with no error anywhere.
  3. Cost the memory instead of calling it large: an 8-byte key plus a 4-byte version is 12 bytes of payload, and an open-addressed table held at a 0.7 load factor costs roughly 17 bytes per entry before per-slot metadata, so 2,000,000 aggregates is tens of megabytes in a native layout and several times that in a runtime that boxes both key and value.
  4. If the distinct set exceeds memory, partition on hash(aggregate_id) mod P and reduce each partition independently. Every event for one aggregate hashes to the same partition, so the per-partition result is exact and the merge is concatenation rather than a second reduction.

Follow-up

  • The payload is a patch rather than a snapshot, so applying only the highest version loses the intermediate changes. What changes in your reduction?
  • How do you detect that version 7 arrived while version 6 was never delivered, and what should the consumer do about the gap?

Find version gaps and relay lag with window functions

Medium · window functions · event tables · frame semantics

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

  1. 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.
  2. 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.
  3. 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.
  4. 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?

Write the update path that detects a concurrent edit

Medium · optimistic concurrency · transactional outbox · audit history

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

  1. 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.
  2. 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.
  3. 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.
  4. 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?

Explain how you would structure a PLC program to handle an emergency stop condition safely.

Medium · Industrial Automation & Control Logic

Approach

  1. Clarify what is being asked and what a complete answer contains.
  2. State your assumptions explicitly before working the problem.
  3. Say what you would check first and why it is the highest-information step.
  4. Work from the requirement backwards to the design.

Follow-up

  • What assumption would you test first?
  • How would you know your answer was wrong?

Walk us through your process for designing a human-machine interface (HMI) that is intuitive for plant operato

Medium · Industrial Automation & Control Logic

Walk us through your process for designing a human-machine interface (HMI) that is intuitive for plant operators.

Approach

  1. Clarify what is being asked and what a complete answer contains.
  2. State your assumptions explicitly before working the problem.
  3. Say what you would check first and why it is the highest-information step.
  4. 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 redundant network topology for a manufacturing facility to ensure zero downtime?

Medium · Systems Integration & Networking

Approach

  1. Fix the scope first: who calls this, how often, and what they do when it fails.
  2. Name the read and write paths separately; they rarely have the same bottleneck.
  3. Choose a partition key and say what query it makes expensive.
  4. 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?

Explain the key differences between Modbus TCP, EtherNet/IP, and Profinet, and when you would use each.

Medium · Systems Integration & Networking

Approach

  1. Say who the caller is and what they do when the call fails halfway.
  2. Define the identity of a request so a retry cannot double-apply it.
  3. Separate accepted, pending, failed and confirmed; they are different facts.
  4. 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 do you secure an industrial control system (ICS) network from external cyber threats without disrupting op

Medium · Systems Integration & Networking

How do you secure an industrial control system (ICS) network from external cyber threats without disrupting operations?

Approach

  1. Say who the caller is and what they do when the call fails halfway.
  2. Define the identity of a request so a retry cannot double-apply it.
  3. Separate accepted, pending, failed and confirmed; they are different facts.
  4. 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?

What is your approach to integrating legacy serial-based hardware into a modern Ethernet-based control system?

Medium · Systems Integration & Networking

Approach

  1. Say who the caller is and what they do when the call fails halfway.
  2. Define the identity of a request so a retry cannot double-apply it.
  3. Separate accepted, pending, failed and confirmed; they are different facts.
  4. 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 do you structure custom application software to ensure it is modular, testable, and maintainable by other

Medium · Software Development & Application Engin

How do you structure custom application software to ensure it is modular, testable, and maintainable by other engineers?

Approach

  1. Clarify what is being asked and what a complete answer contains.
  2. State your assumptions explicitly before working the problem.
  3. Say what you would check first and why it is the highest-information step.
  4. 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 custom software tool or script you wrote to automate a repetitive engineering or manufacturing task

Medium · Software Development & Application Engin

Describe a custom software tool or script you wrote to automate a repetitive engineering or manufacturing task.

Approach

  1. Clarify what is being asked and what a complete answer contains.
  2. State your assumptions explicitly before working the problem.
  3. Say what you would check first and why it is the highest-information step.
  4. 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 manage software version control when working with proprietary industrial programming environments?

Medium · Software Development & Application Engin

Approach

  1. Clarify what is being asked and what a complete answer contains.
  2. State your assumptions explicitly before working the problem.
  3. Say what you would check first and why it is the highest-information step.
  4. Work from the requirement backwards to the design.

Follow-up

  • What assumption would you test first?
  • How would you know your answer was wrong?

Explain how you would design a database schema to log and analyze real-time telemetry data from industrial equ

Medium · Software Development & Application Engin

Explain how you would design a database schema to log and analyze real-time telemetry data from industrial equipment.

Approach

  1. Fix the scope first: who calls this, how often, and what they do when it fails.
  2. Name the read and write paths separately; they rarely have the same bottleneck.
  3. Choose a partition key and say what query it makes expensive.
  4. 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 strategies do you use to debug a synchronization issue between multiple servo drives?

Medium · Industrial Automation & Control Logic

Approach

  1. Establish what changed and when, before forming any theory.
  2. Pick a bisection that eliminates candidates whichever way it turns out.
  3. Check the instrumentation before believing the symptom.
  4. 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?

Suggested practice checklist

Built from the rounds and topics Komline-Sanderson candidates report.

Day 1 — Map the Komline-Sanderson loop

  • Write out the reported sequence: Initial Alignment, Deep Technical Evaluations, Panel and Onsite Stages.
  • 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.

Day 2 — Work CNC Programming (Computer Numerical Control)

  • Spend the session on CNC Programming (Computer Numerical Control), which Komline-Sanderson candidates report being tested on.
  • Write one worked example in CNC Programming (Computer Numerical Control) and time yourself on it.

Deliverable: One timed worked example in CNC Programming (Computer Numerical Control).

Day 3 — Work Network Engineering

  • Spend the session on Network Engineering, which Komline-Sanderson candidates report being tested on.
  • Write one worked example in Network Engineering and time yourself on it.

Deliverable: One timed worked example in Network Engineering.

Day 4 — Work Applications Engineering

  • Spend the session on Applications Engineering, which Komline-Sanderson candidates report being tested on.
  • Write one worked example in Applications Engineering and time yourself on it.

Deliverable: One timed worked example in Applications Engineering.

Day 5 — Answer out loud: Industrial Automation & Control Logic

  • Answer aloud, timed: Explain how you would structure a PLC program to handle an emergency stop condition safely.
  • Answer aloud, timed: Describe your experience with G-code and M-code optimization for CNC machinery.

Deliverable: Spoken answers to 2 reported Industrial Automation & Control Logic question(s), under time.

Day 6 — Answer out loud: Systems Integration & Networking

  • Answer aloud, timed: How would you design a redundant network topology for a manufacturing facility to ensure zero downtime?
  • Answer aloud, timed: Explain the key differences between Modbus TCP, EtherNet/IP, and Profinet, and when you would use each.

Deliverable: Spoken answers to 2 reported Systems Integration & Networking question(s), under time.

Day 7 — Answer out loud: Software Development & Application Engineering

  • Answer aloud, timed: How do you structure custom application software to ensure it is modular, testable, and maintainable by other engineers?
  • Answer aloud, timed: Describe a custom software tool or script you wrote to automate a repetitive engineering or manufacturing task.

Deliverable: Spoken answers to 2 reported Software Development & Application Engineering question(s), under time.

Behavioural preparation

Behavioural rounds judge the decision you made and what it cost.

Describe your experience with G-code and M-code optimization for CNC machinery.

Medium · Industrial Automation & Control Logic

Approach

  1. Pick a story where you made the decision, not one where you watched it.
  2. State the situation in two sentences and spend the rest on the reasoning.
  3. Give the blast radius: what could have broken, and what you measured.
  4. 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 signal noise or latency when reading analog sensor data in a control loop?

Medium · Industrial Automation & Control Logic

Approach

  1. Pick a story where you made the decision, not one where you watched it.
  2. State the situation in two sentences and spend the rest on the reasoning.
  3. Give the blast radius: what could have broken, and what you measured.
  4. 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 troubleshoot a packet loss issue on an active production network.

Medium · Systems Integration & Networking

Approach

  1. Pick a story where you made the decision, not one where you watched it.
  2. State the situation in two sentences and spend the rest on the reasoning.
  3. Give the blast radius: what could have broken, and what you measured.
  4. 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 approach to conducting code reviews for safety-critical control software?

Medium · Software Development & Application Engin

Approach

  1. Pick a story where you made the decision, not one where you watched it.
  2. State the situation in two sentences and spend the rest on the reasoning.
  3. Give the blast radius: what could have broken, and what you measured.
  4. 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 collaborate with a mechanical or chemical engineer to resolve a complex produc

Medium · Behavioral & Project Management

Describe a time when you had to collaborate with a mechanical or chemical engineer to resolve a complex product defect.

Approach

  1. Pick a story where you made the decision, not one where you watched it.
  2. State the situation in two sentences and spend the rest on the reasoning.
  3. Give the blast radius: what could have broken, and what you measured.
  4. 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 a situation where a field technician reports a software bug on-site that you cannot replicat

Medium · Behavioral & Project Management

How do you handle a situation where a field technician reports a software bug on-site that you cannot replicate in the lab?

Approach

  1. Pick a story where you made the decision, not one where you watched it.
  2. State the situation in two sentences and spend the rest on the reasoning.
  3. Give the blast radius: what could have broken, and what you measured.
  4. 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?

Give an example of a time you had to explain a highly technical software issue to a non-technical customer or

Medium · Behavioral & Project Management

Give an example of a time you had to explain a highly technical software issue to a non-technical customer or stakeholder.

Approach

  1. Pick a story where you made the decision, not one where you watched it.
  2. State the situation in two sentences and spend the rest on the reasoning.
  3. Give the blast radius: what could have broken, and what you measured.
  4. 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 balance competing priorities or manage multiple project deadlines simult

Medium · Behavioral & Project Management

Describe a situation where you had to balance competing priorities or manage multiple project deadlines simultaneously.

Approach

  1. Pick a story where you made the decision, not one where you watched it.
  2. State the situation in two sentences and spend the rest on the reasoning.
  3. Give the blast radius: what could have broken, and what you measured.
  4. 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?