cswork / libraryOpen practice workspace

Interview guides · DNV

DNV Software Engineer Interview Guide

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

The 60-second brief

As a Software Engineer at DNV, you play a direct role in building digital solutions that safeguard life, property, and the environment. DNV is a global assurance and risk management organization operating extensively across energy, renewables, maritime, and oil and gas sectors. Software engineers here do not build standard consumer apps; instead, you build high-reliability, data-intensive applications, engineering simulation tools, pipeline software solutions, and energy transition analytics platforms that power critical global infrastructure. Your work directly impacts technical consultants, energy operators, and field inspectors worldwide. Whether you are modernizing core backend systems using.NET, developing data pipelines, or designing intuitive user interfaces, you will be expected to produce maintainable, highly reliable code.

This guide is scoped to a Software Engineer candidate at DNV.

Focus areas

  • Technical interview fundamentals
  • Communication skills
  • Databases - SQL

The DNV interview process

DNV candidates report 5 rounds over 4-6 weeks. The stages below are what candidates describe, not a published process.

Online Application

Candidates begin by submitting an online application for the Software Engineer position.

What to demonstrate

  • Candidates begin by submitting an online application for the Software Engineer position
  • Depth in Technical interview fundamentals

How to prepare

  • Answer aloud and timed: How do you choose between relational databases (SQL) and non-relational databases (MongoDB) for a new application feature?
  • Answer aloud and timed: Explain your experience with Agile methodologies, including daily standups, sprint planning, and retrospective meetings.

Initial Screening

Includes an automated video interview where candidates record answers to pre-set questions.

What to demonstrate

  • Includes an automated video interview where candidates record answers to pre-set questions
  • Depth in Technical interview fundamentals

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.

Assessments

Candidates complete psychometric, cognitive, or gamified assessments to evaluate various skills.

What to demonstrate

  • Candidates complete psychometric, cognitive, or gamified assessments to evaluate various skills
  • Depth in Technical interview fundamentals

How to prepare

  • Answer aloud and timed: How do you optimize database queries or structure data collections to ensure efficient retrieval under high load?
  • Answer aloud and timed: Walk us through a recent software project you led or contributed to significantly. What was the architecture and your specific role?

Technical and Managerial Discussions

Live discussions over video or in-person with line managers, senior engineers, and HR representatives.

What to demonstrate

  • Live discussions over video or in-person with line managers, senior engineers, and HR representatives
  • Depth in Technical interview fundamentals

How to prepare

  • Answer aloud and timed: Tell us about a technical challenge you encountered during a software deployment and how you resolved it.
  • Answer aloud and timed: How do you handle changing requirements or shifting priorities during an active software development cycle?

Assessment Days

Structured group discussions and technical presentations may occur in certain locations or graduate programs.

What to demonstrate

  • Structured group discussions and technical presentations may occur in certain locations or graduate programs
  • Depth in Technical interview fundamentals

How to prepare

  • Answer aloud and timed: Describe a project where you had to learn a new programming language or framework on a tight deadline.
  • Answer aloud and timed: What testing methodologies do you incorporate into your daily workflow to ensure code quality?

Where candidates lose points

Prepare for psychometric and cognitive testing

Many candidate pipelines incorporate automated cognitive, numerical, or personality assessments early in the process. Take practice tests beforehand to familiarize yourself with time-pressured logical and gamified questions.

Structure project stories clearly

When asked about past experience, use the STAR approach (Situation, Task, Action, Result). Explicitly highlight your individual code contributions, technologies used, and team outcomes.

Research DNV's primary domain focus

Demonstrate that you understand DNV's business footprint in energy transition, maritime safety, and pipeline integrity software. Showing genuine interest in these domains distinguishes you from generic software applicants.

Questions & practice

If assigned a software project with ambiguous requirements, what initial steps do you take to define the techn

Medium · Case Studies & Situational Scenarios

If assigned a software project with ambiguous requirements, what initial steps do you take to define the technical scope?

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?

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?

Archive a resource graph without breaking live references or recursing

Medium · graph traversal · topological order · tenant isolation

Resources reference other resources within a tenant; for the largest tenant the reference table holds up to 2,000,000 nodes and 8,000,000 edges. Archiving a resource must archive everything reachable from it that nothing outside the set still references, refuse when a live external referrer exists, and terminate when references form cycles, which they legitimately do. Produce the archive order and the refusal list, targeting O(V+E). Say what stops the traversal crossing a tenant boundary, and why recursion is the wrong control structure at this size.

Approach

  1. Load the subgraph with the tenant predicate on both endpoints of the edge, not only on the side you started from. Scoping the left table alone is the classic cross-tenant leak: one mis-entered edge then pulls another tenant's resources into the traversal and, worse, into the archive.
  2. Traverse iteratively with an explicit stack. A 2,000,000-node graph can hold a chain deep enough to exhaust a native stack in the low tens of thousands of frames, and that failure is a process crash rather than an error you can return.
  3. Treat cycles as data rather than corruption: compute strongly connected components with Tarjan in O(V+E) using its own explicit stack, then condense. The condensation is a DAG, so a topological order over it gives the archive order, and every member of a component archives in one transaction because no order within a cycle is valid.
  4. Decide refusals with reverse edges. A candidate is archivable only if every in-edge originates inside the candidate set, so build the transpose or count in-degrees restricted to the visited set, and emit each blocked resource with the id of the external referrer, which is the only part of the answer an operator can act on.

Follow-up

  • The graph is read in one query and the archive writes a minute later. What can change in between, and how do you make the write safe?
  • The candidate set is 400,000 resources. Is that one transaction, and if not, what does a half-finished archive look like to a reader?

How do you choose between relational databases (SQL) and non-relational databases (MongoDB) for a new applicat

Medium · Technical & Software Engineering Fundame

How do you choose between relational databases (SQL) and non-relational databases (MongoDB) for a new application feature?

Approach

  1. Name the grain you start from and join outward from it.
  2. Check whether any join is one-to-many before aggregating, or the sums inflate.
  3. Say which index the query would use, and what makes it unusable.
  4. Handle the rows that do not match: that is usually the actual question.

Follow-up

  • How does the query change if that join becomes one-to-many?
  • What happens to this when the table is ten times larger?

Why do you want to join DNV specifically, and how does our work in energy transition and risk assurance align

Medium · Behavioral & Team Collaboration

Why do you want to join DNV specifically, and how does our work in energy transition and risk assurance align with your goals?

Approach

  1. Name the grain you start from and join outward from it.
  2. Check whether any join is one-to-many before aggregating, or the sums inflate.
  3. Say which index the query would use, and what makes it unusable.
  4. Handle the rows that do not match: that is usually the actual question.

Follow-up

  • How does the query change if that join becomes one-to-many?
  • What happens to this when the table is ten times larger?

Walk us through your deployment process using version control (Git) and continuous integration pipelines (Jenk

Medium · Technical & Software Engineering Fundame

Walk us through your deployment process using version control (Git) and continuous integration pipelines (Jenkins).

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 are the core object-oriented principles you rely on when developing backend services in frameworks like.N

Medium · Technical & Software Engineering Fundame

What are the core object-oriented principles you rely on when developing backend services in frameworks like.NET?

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 optimize database queries or structure data collections to ensure efficient retrieval under high lo

Medium · Technical & Software Engineering Fundame

How do you optimize database queries or structure data collections to ensure efficient retrieval under high load?

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 a recent software project you led or contributed to significantly. What was the architecture a

Medium · Project Deep Dives & Applied Experience

Walk us through a recent software project you led or contributed to significantly. What was the architecture and your specific role?

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?

Tell us about a technical challenge you encountered during a software deployment and how you resolved it.

Medium · Project Deep Dives & Applied Experience

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 project where you had to learn a new programming language or framework on a tight deadline.

Medium · Project Deep Dives & Applied Experience

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?

What testing methodologies do you incorporate into your daily workflow to ensure code quality?

Medium · Project Deep Dives & Applied Experience

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?

Given a operational scenario with competing stakeholder requirements, how would you prioritize software featur

Medium · Case Studies & Situational Scenarios

Given a operational scenario with competing stakeholder requirements, how would you prioritize software features?

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 communicate a technical system delay or bug to a non-technical manager or external client?

Medium · Case Studies & Situational Scenarios

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?

Exports duplicate a row range about once a week

Hard · leases · clock skew · idempotency

Roughly once a week an export writes a file containing a duplicated range of rows. The affected job_run rows show attempt = 1, status = succeeded, one started_at, and a lease_owner naming a different host from the one whose logs show the job starting. Leases last 30 seconds and are heartbeated every 10 from inside the handler; lease_expires_at is computed on the worker and compared against the database's now(). Find the mechanism, and give a fix that holds even if you cannot fix the clocks.

Approach

  1. Start from the fact that eliminates the obvious answer. attempt = 1 means no retry was recorded, so this is not a re-run after failure; two workers ran the same row concurrently and the takeover path never touched the counter. lease_owner naming a host other than the one that started the job is the same statement from the other side.
  2. Enumerate the mechanisms that cause a premature takeover, then find the signal that separates them. Either the lease genuinely expired because the heartbeat did not fire, which is what happens when the heartbeat runs on the handler's own thread and the handler makes a long blocking call, or it only appeared expired because two clocks disagree, since lease_expires_at is written from the worker's clock and evaluated against the database's. The discriminator is the distribution: incidents clustered on the longest exports indict the heartbeat, incidents clustered on one host indict skew. Measure both, and measure each host's offset against the database directly.
  3. Read the reclaim query precisely. In PostgreSQL now() is transaction start time, not statement time, so a reclaimer holding a long transaction compares against an older timestamp than expected; clock_timestamp() is the statement-time function. This is worth ruling in or out before you redesign anything, because it changes which rows look expired.
  4. Remove the second clock rather than trying to synchronise it. Issue and extend the lease in the database, with lease_expires_at = now() + interval '30 seconds' in both the claim and the heartbeat, so exactly one clock is ever compared and worker skew stops mattering to this predicate.

Follow-up

  • The displaced worker has already streamed half the file to object storage. What makes that side effect safe to repeat?
  • You now count takeovers. What alert fires on that counter, and at what threshold?

Suggested practice checklist

Built from the rounds and topics DNV candidates report.

Day 1 — Map the DNV loop

  • Write out the reported sequence: Online Application, Initial Screening, Assessments, Technical and Managerial Discussions, Assessment Days.
  • 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.

Day 2 — Work Technical interview fundamentals

  • Spend the session on Technical interview fundamentals, which DNV candidates report being tested on.
  • Write one worked example in Technical interview fundamentals and time yourself on it.

Deliverable: One timed worked example in Technical interview fundamentals.

Day 3 — Work Communication skills

  • Spend the session on Communication skills, which DNV candidates report being tested on.
  • Write one worked example in Communication skills and time yourself on it.

Deliverable: One timed worked example in Communication skills.

Day 4 — Work Databases - SQL

  • Spend the session on Databases - SQL, which DNV candidates report being tested on.
  • Write one worked example in Databases - SQL and time yourself on it.

Deliverable: One timed worked example in Databases - SQL.

Day 5 — Answer out loud: Technical & Software Engineering Fundamentals

  • Answer aloud, timed: How do you choose between relational databases (SQL) and non-relational databases (MongoDB) for a new application feature?
  • Answer aloud, timed: Explain your experience with Agile methodologies, including daily standups, sprint planning, and retrospective meetings.

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

Day 6 — Answer out loud: Project Deep Dives & Applied Experience

  • Answer aloud, timed: Walk us through a recent software project you led or contributed to significantly. What was the architecture and your specific role?
  • Answer aloud, timed: Tell us about a technical challenge you encountered during a software deployment and how you resolved it.

Deliverable: Spoken answers to 2 reported Project Deep Dives & Applied Experience question(s), under time.

Day 7 — Answer out loud: Behavioral & Team Collaboration

  • Answer aloud, timed: Why do you want to join DNV specifically, and how does our work in energy transition and risk assurance align with your goals?
  • Answer aloud, timed: Describe a situation where you had to collaborate with team members across different time zones or cultural backgrounds.

Deliverable: Spoken answers to 2 reported Behavioral & Team Collaboration question(s), under time.

Behavioural preparation

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

Explain your experience with Agile methodologies, including daily standups, sprint planning, and retrospective

Medium · Technical & Software Engineering Fundame

Explain your experience with Agile methodologies, including daily standups, sprint planning, and retrospective meetings.

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 changing requirements or shifting priorities during an active software development cycle?

Medium · Project Deep Dives & Applied Experience

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 collaborate with team members across different time zones or cultural ba

Medium · Behavioral & Team Collaboration

Describe a situation where you had to collaborate with team members across different time zones or cultural backgrounds.

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?

Tell us about a time you had a technical disagreement with a colleague or lead engineer. How did you handle it

Medium · Behavioral & Team Collaboration

Tell us about a time you had a technical disagreement with a colleague or lead engineer. How did you handle it?

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 manage your time and prioritize tasks when balancing multiple software features or bugs?

Medium · Behavioral & Team Collaboration

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 scenario where a project was falling behind schedule. What proactive steps did you take to mitigate

Medium · Behavioral & Team Collaboration

Describe a scenario where a project was falling behind schedule. What proactive steps did you take to mitigate the delay?

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?