As a Software Engineer at Doosan, you will play a pivotal role in shaping the technological landscape of the company. This position is vital not only because it influences the development and optimization of cutting-edge software solutions but also because it directly impacts the efficiency and effectiveness of various operational processes within the organization. Your work will be fundamental in ensuring that Doosan remains competitive in the global market, contributing to products that power industries and enhance infrastructure. In this role, you will engage with complex systems and collaborate with cross-functional teams to design, implement, and maintain software applications. This includes working on innovative projects, such as fuel cell technology and advanced manufacturing systems, which are central to Doosan's mission of sustainability and technological advancement. Expect to face challenges that will require both your technical expertise and your problem-solving capabilities, providing a rewarding experience as you contribute to meaningful projects that make a difference.
Phone Screening
reportedA recruiter will assess your background and interest in the position.
What to demonstrate
- A recruiter will assess your background and interest in the position
- Depth in Technical Interview Rounds
How to prepare
- Be able to walk your CV end to end in two minutes, and say why this company specifically.
- Have your salary expectations, notice period and location constraints ready, and ask for the rest of the loop in writing.
Technical Interviews
reportedInvolve coding challenges or problem-solving scenarios to demonstrate your skills.
What to demonstrate
- Involve coding challenges or problem-solving scenarios to demonstrate your skills
- Depth in Technical Interview Rounds
How to prepare
- Answer aloud and timed: Describe a challenging technical problem you resolved in a past project.
- Answer aloud and timed: How do you approach debugging an application?
In-Person Interviews
reportedMultiple sessions with various team members to interact and gain insights into team dynamics.
What to demonstrate
- Multiple sessions with various team members to interact and gain insights into team dynamics
- Depth in Technical Interview Rounds
How to prepare
- Answer aloud and timed: What tools do you use for version control and why?
- Answer aloud and timed: Describe a situation where you had to work as part of a team to achieve a goal.
PracHub editorial advice for the preparation topics above.
Know your projects
Be prepared to discuss your past projects in detail, including your specific contributions and the technologies used.
Practice coding
Utilize platforms like LeetCode or HackerRank to sharpen your coding skills before interviews.
Ask insightful questions
Prepare thoughtful questions for your interviewers that demonstrate your interest in the role and the company.
Be authentic
Show your genuine passion for technology and how it aligns with your career aspirations.
Choose a category, try a prompt, then open its approach, worked solution or follow-up when you need it.
Write a function to reverse a string.
Write a function to reverse a string.
Approach
- Restate the input: its shape, its size, and what is guaranteed about it.
- Name the brute-force solution and its complexity before improving on it.
- Choose the data structure from the access pattern, not from familiarity.
- State the target complexity and say which constraint rules the naive version out.
Follow-up
- How does this change if the input no longer fits in memory?
- What is the worst case, and how likely is it on real data?
How would you implement a binary search algorithm?
How would you implement a binary search algorithm?
Approach
- Restate the input: its shape, its size, and what is guaranteed about it.
- Name the brute-force solution and its complexity before improving on it.
- Choose the data structure from the access pattern, not from familiarity.
- State the target complexity and say which constraint rules the naive version out.
Follow-up
- How does this change if the input no longer fits in memory?
- What is the worst case, and how likely is it on real data?
Explain the differences between a stack and a queue and provide examples of their use cases.
Explain the differences between a stack and a queue and provide examples of their use cases.
Approach
- Restate the input: its shape, its size, and what is guaranteed about it.
- Name the brute-force solution and its complexity before improving on it.
- Choose the data structure from the access pattern, not from familiarity.
- State the target complexity and say which constraint rules the naive version out.
Follow-up
- How does this change if the input no longer fits in memory?
- What is the worst case, and how likely is it on real data?
Can you optimize this code for better performance? [Provide a snippet for them to analyze.]
Can you optimize this code for better performance? [Provide a snippet for them to analyze.]
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?
Discuss time complexity and space complexity in your solution.
Discuss time complexity and space complexity in your solution.
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?
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?
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?
What programming languages are you most comfortable with, and why?
What programming languages are you most comfortable with, and why?
Approach
- Clarify what is being asked and what a complete answer contains.
- State your assumptions explicitly before working the problem.
- Say what you would check first and why it is the highest-information step.
- Work from the requirement backwards to the design.
Follow-up
- What assumption would you test first?
- How would you know your answer was wrong?
Can you explain the software development lifecycle?
Can you explain the software development lifecycle?
Approach
- Clarify what is being asked and what a complete answer contains.
- State your assumptions explicitly before working the problem.
- Say what you would check first and why it is the highest-information step.
- Work from the requirement backwards to the design.
Follow-up
- What assumption would you test first?
- How would you know your answer was wrong?
Describe a challenging technical problem you resolved in a past project.
Describe a challenging technical problem you resolved in a past project.
Approach
- Clarify what is being asked and what a complete answer contains.
- State your assumptions explicitly before working the problem.
- Say what you would check first and why it is the highest-information step.
- Work from the requirement backwards to the design.
Follow-up
- What assumption would you test first?
- How would you know your answer was wrong?
What tools do you use for version control and why?
What tools do you use for version control and why?
Approach
- Clarify what is being asked and what a complete answer contains.
- State your assumptions explicitly before working the problem.
- Say what you would check first and why it is the highest-information step.
- Work from the requirement backwards to the design.
Follow-up
- What assumption would you test first?
- How would you know your answer was wrong?
Walk us through your thought process for a project from inception to completion.
Walk us through your thought process for a project from inception to completion.
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?
Given a specific problem scenario, how would you approach finding a solution?
Given a specific problem scenario, how would you approach finding a solution?
Approach
- Clarify what is being asked and what a complete answer contains.
- State your assumptions explicitly before working the problem.
- Say what you would check first and why it is the highest-information step.
- Work from the requirement backwards to the design.
Follow-up
- What assumption would you test first?
- How would you know your answer was wrong?
How do you ensure that your solutions are scalable and maintainable?
How do you ensure that your solutions are scalable and maintainable?
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?
Provide an example of a project where you had to learn a new technology quickly.
Provide an example of a project where you had to learn a new technology quickly.
Approach
- Clarify what is being asked and what a complete answer contains.
- State your assumptions explicitly before working the problem.
- Say what you would check first and why it is the highest-information step.
- Work from the requirement backwards to the design.
Follow-up
- What assumption would you test first?
- How would you know your answer was wrong?
How do you approach debugging an application?
How do you approach debugging an application?
Approach
- Establish what changed and when, before forming any theory.
- Pick a bisection that eliminates candidates whichever way it turns out.
- Check the instrumentation before believing the symptom.
- Separate the trigger from the cause; the deploy is rarely the bug.
Follow-up
- What would you look at first, and what would it rule out?
- How would you tell a cause from a coincidence here?
Built from the rounds and topics Doosan candidates report.
Prepare, practise & reflect
One practical outcome each day. Spend longer where you need it.
0 / 7 done01Map the Doosan loop
- Write out the reported sequence: Phone Screening, Technical Interviews, In-Person Interviews.
- For each round, write one sentence on what it is judging, from the description above, and mark the one you are least ready for.
Deliverable: A one-page map of the 3 reported rounds, with the weakest marked.
02Work Technical Interview Rounds
- Spend the session on Technical Interview Rounds, which Doosan candidates report being tested on.
- Write one worked example in Technical Interview Rounds and time yourself on it.
Deliverable: One timed worked example in Technical Interview Rounds.
03Work Domain Knowledge: Fuel Cell Technology
- Spend the session on Domain Knowledge: Fuel Cell Technology, which Doosan candidates report being tested on.
- Write one worked example in Domain Knowledge: Fuel Cell Technology and time yourself on it.
Deliverable: One timed worked example in Domain Knowledge: Fuel Cell Technology.
04Work Professional Experience to Requirements Mapping
- Spend the session on Professional Experience to Requirements Mapping, which Doosan candidates report being tested on.
- Write one worked example in Professional Experience to Requirements Mapping and time yourself on it.
Deliverable: One timed worked example in Professional Experience to Requirements Mapping.
05Answer out loud: Technical / Domain Questions
- Answer aloud, timed: What programming languages are you most comfortable with, and why?
- Answer aloud, timed: Can you explain the software development lifecycle?
Deliverable: Spoken answers to 2 reported Technical / Domain Questions question(s), under time.
06Answer out loud: Behavioral / Leadership Questions
- Answer aloud, timed: Describe a situation where you had to work as part of a team to achieve a goal.
- Answer aloud, timed: How do you handle conflicts within a team?
Deliverable: Spoken answers to 2 reported Behavioral / Leadership Questions question(s), under time.
07Answer out loud: Problem-Solving / Case Studies
- Answer aloud, timed: Walk us through your thought process for a project from inception to completion.
- Answer aloud, timed: Given a specific problem scenario, how would you approach finding a solution?
Deliverable: Spoken answers to 2 reported Problem-Solving / Case Studies question(s), under time.
Expand any day for tasks and deliverables. Your progress is saved on this device.
Behavioural rounds judge the decision you made and what it cost.
Describe a situation where you had to work as part of a team to achieve a goal.
Describe a situation where you had to work as part of a team to achieve a goal.
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 conflicts within a team?
How do you handle conflicts within a team?
Approach
- Pick a story where you made the decision, not one where you watched it.
- State the situation in two sentences and spend the rest on the reasoning.
- Give the blast radius: what could have broken, and what you measured.
- Name the disagreement and how you resolved it with evidence.
Follow-up
- What would you do differently if you ran that again?
- How did you know your change caused the improvement?
Can you provide an example of a time you took the initiative to solve a problem?
Can you provide an example of a time you took the initiative to solve a problem?
Approach
- Pick a story where you made the decision, not one where you watched it.
- State the situation in two sentences and spend the rest on the reasoning.
- Give the blast radius: what could have broken, and what you measured.
- Name the disagreement and how you resolved it with evidence.
Follow-up
- What would you do differently if you ran that again?
- How did you know your change caused the improvement?
What motivates you in your work?
What motivates you in your work?
Approach
- Pick a story where you made the decision, not one where you watched it.
- State the situation in two sentences and spend the rest on the reasoning.
- Give the blast radius: what could have broken, and what you measured.
- Name the disagreement and how you resolved it with evidence.
Follow-up
- What would you do differently if you ran that again?
- How did you know your change caused the improvement?
How do you prioritize tasks when faced with multiple deadlines?
How do you prioritize tasks when faced with multiple deadlines?
Approach
- Pick a story where you made the decision, not one where you watched it.
- State the situation in two sentences and spend the rest on the reasoning.
- Give the blast radius: what could have broken, and what you measured.
- Name the disagreement and how you resolved it with evidence.
Follow-up
- What would you do differently if you ran that again?
- How did you know your change caused the improvement?
Describe a time when you had to adapt your solution based on feedback or changing requirements.
Describe a time when you had to adapt your solution based on feedback or changing requirements.
Approach
- Pick a story where you made the decision, not one where you watched it.
- State the situation in two sentences and spend the rest on the reasoning.
- Give the blast radius: what could have broken, and what you measured.
- Name the disagreement and how you resolved it with evidence.
Follow-up
- What would you do differently if you ran that again?
- How did you know your change caused the improvement?
- 01
Describe a situation where you had to work as part of a team to achieve a goal.
- 02
How do you handle conflicts within a team?
- 03
Can you provide an example of a time you took the initiative to solve a problem?
- 04
What motivates you in your work?
How difficult is the interview process, and how much preparation time do I need?
The interview process at Doosan is generally considered average in difficulty. Candidates typically spend a few weeks preparing, focusing on technical skills, problem-solving, and understanding the company culture.
Doosan Software Engineer candidate reports ↗What differentiates successful candidates?
Successful candidates often showcase not only strong technical skills but also the ability to communicate effectively and work collaboratively within teams. Demonstrating alignment with Doosan's values can also set you apart.
Doosan Software Engineer candidate reports ↗What is the culture and working style at Doosan?
Doosan values teamwork, innovation, and a commitment to excellence. Employees are encouraged to share ideas and contribute to projects actively, fostering a collaborative environment.
Doosan Software Engineer candidate reports ↗What is the typical timeline from the initial screen to an offer?
The timeline can vary, but candidates often receive feedback within 2-3 weeks after their final interviews. It’s important to stay engaged throughout the process.
Doosan Software Engineer candidate reports ↗Are there remote work options available?
While many roles may allow for flexible arrangements, it's best to discuss specific expectations during your interviews, as policies may vary by team and location.
Doosan Software Engineer candidate reports ↗What topics does Doosan test in interviews?
Doosan interviews most often cover Project Management (Role Fundamentals), Technical Interview Rounds, Interview Process (Multi-round Structure), Domain Knowledge: Fuel Cell Technology, and Behavioral Interviewing. The exact emphasis depends on the specific role you apply for.
Doosan 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.
- 01Doosan 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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