As a Software Engineer at HN Services Portugal, you play a pivotal role in designing, developing, and maintaining software solutions that support critical business functions. Your work directly influences the performance and reliability of products that serve a diverse clientele, ensuring that they operate seamlessly in a competitive landscape. This position is not only about coding; it encompasses problem-solving, collaboration, and innovation, all of which are essential in delivering high-quality software that meets user needs. Your contributions will impact various product lines, reflecting the complexity and scale at which HN Services Portugal operates. You will engage with cross-functional teams to tackle challenges related to system architecture, user experience, and operational efficiency. This role is both challenging and rewarding, providing you with opportunities to develop your skills, contribute to exciting projects, and influence the technological direction of the company.
Initial Screening
reportedA brief phone interview to discuss your background and interest in the role.
What to demonstrate
- A brief phone interview to discuss your background and interest in the role
- Depth in Algorithmic problem solving
How to prepare
- Be able to walk your CV end to end in two minutes, and say why this company specifically.
- Have your salary expectations, notice period and location constraints ready, and ask for the rest of the loop in writing.
Technical Assessments
reportedA series of logic and coding tests to gauge your problem-solving skills and technical proficiency.
What to demonstrate
- A series of logic and coding tests to gauge your problem-solving skills and technical proficiency
- Depth in Algorithmic problem solving
How to prepare
- Answer aloud and timed: How do you approach debugging a complex issue in your code?
- Answer aloud and timed: Can you discuss your experience with version control systems like Git?
PracHub editorial advice for the preparation topics above.
Practice Coding
Regularly work on coding challenges to sharpen your problem-solving skills. Resources like LeetCode or HackerRank can be helpful.
Understand the Company Culture
Familiarize yourself with HN Services Portugal’s values and culture. Demonstrating alignment during your interview can enhance your candidacy.
Prepare Questions
Have thoughtful questions ready for your interviewers. This shows your interest in the role and helps you assess if the company is the right fit for you.
Stay Calm Under Pressure
Interviews can be stressful, but maintaining composure will help you think clearly and respond effectively.
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 linked list.
Write a function to reverse a linked list.
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?
Given a list of integers, find the two numbers that add up to a specific target.
Given a list of integers, find the two numbers that add up to a specific target.
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 concept of Big O notation and provide examples of its application.
Explain the concept of Big O notation and provide examples of its application.
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?
Solve a problem involving dynamic programming and explain your thought process.
Solve a problem involving dynamic programming and explain your thought process.
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 why the owner filter ignores the listing index
The only index on resource is (tenant_id, status, updated_at DESC, resource_id DESC). A new endpoint returns one user's resources across all statuses, newest created first: WHERE tenant_id = $1 AND owner_user_id = $2 ORDER BY created_at DESC LIMIT 20. On a tenant with 2M rows it takes 900 ms and EXPLAIN shows a sort above a large scan. Explain precisely why the existing index cannot serve it, give the index that can, and state which of these the new index still will not help: owner_user_id alone across tenants; the same query ordered by updated_at. PostgreSQL 16.
Approach
- Separate the two jobs an index does. For filtering, a composite btree is seekable only on a left prefix, so with no predicate on status the scan can at best range over tenant_id and test owner_user_id per row; PostgreSQL 16 has no btree skip scan to jump the unconstrained column.
- For ordering, the index is sorted by (status, updated_at) within a tenant and not by created_at, so the LIMIT cannot stop early: every matching row is read and then sorted. That is the 'Sort Method: top-N heapsort' line, and it is why the plan reads 2M rows to answer with 20.
- Derive the replacement from the access path — equality, equality, then the ordering column: CREATE INDEX CONCURRENTLY ON resource (tenant_id, owner_user_id, created_at DESC). The scan seeks to the (tenant, owner) range and walks 20 entries in order, so the Sort node disappears along with the row-read.
- Treat INCLUDE (title, status) as conditional, not free. An index-only scan still visits the heap for any row whose page is not marked all-visible, so on a table taking 1.2k writes/second the win depends on autovacuum keeping the visibility map current, and the wider index costs more on every insert.
Follow-up
- 90% of rows are status='active'. Would a partial index WHERE status = 'active' change your answer, and for which of the three queries?
- A dashboard runs this for 40 owners in one page load. What changes about the design?
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?
Explain a recent project where you utilized [specific technology].
Explain a recent project where you utilized [specific technology].
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 are the key differences between [technology A] and [technology B]?
What are the key differences between [technology A] and [technology B]?
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 how you ensure the quality of your code through testing.
Describe how you ensure the quality of your code through testing.
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 faced and how you resolved it.
Describe a challenging technical problem you faced and how you resolved it.
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 prioritize tasks when working on multiple projects?
How do you prioritize tasks when working on multiple projects?
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 steps would you take to improve the performance of a slow application?
What steps would you take to improve the performance of a slow application?
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 a complex issue in your code?
How do you approach debugging a complex issue in your code?
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 HN Services Portugal candidates report.
Prepare, practise & reflect
One practical outcome each day. Spend longer where you need it.
0 / 7 done01Map the HN Services Portugal loop
- Write out the reported sequence: Initial Screening, Technical Assessments.
- For each round, write one sentence on what it is judging, from the description above, and mark the one you are least ready for.
Deliverable: A one-page map of the 2 reported rounds, with the weakest marked.
02Work Algorithmic problem solving
- Spend the session on Algorithmic problem solving, which HN Services Portugal candidates report being tested on.
- Write one worked example in Algorithmic problem solving and time yourself on it.
Deliverable: One timed worked example in Algorithmic problem solving.
03Work Logic testing (reasoning puzzles)
- Spend the session on Logic testing (reasoning puzzles), which HN Services Portugal candidates report being tested on.
- Write one worked example in Logic testing (reasoning puzzles) and time yourself on it.
Deliverable: One timed worked example in Logic testing (reasoning puzzles).
04Work Data structures & algorithms concepts
- Spend the session on Data structures & algorithms concepts, which HN Services Portugal candidates report being tested on.
- Write one worked example in Data structures & algorithms concepts and time yourself on it.
Deliverable: One timed worked example in Data structures & algorithms concepts.
05Answer out loud: Technical / Domain Questions
- Answer aloud, timed: Explain a recent project where you utilized [specific technology].
- Answer aloud, timed: What are the key differences between [technology A] and [technology B]?
Deliverable: Spoken answers to 2 reported Technical / Domain Questions question(s), under time.
06Answer out loud: Problem-solving / Case Studies
- Answer aloud, timed: Describe a challenging technical problem you faced and how you resolved it.
- Answer aloud, timed: How do you prioritize tasks when working on multiple projects?
Deliverable: Spoken answers to 2 reported Problem-solving / Case Studies question(s), under time.
07Answer out loud: Behavioral / Leadership Questions
- Answer aloud, timed: How do you handle feedback from peers or supervisors?
- Answer aloud, timed: Describe a time when you had to lead a project and the outcome.
Deliverable: Spoken answers to 2 reported Behavioral / Leadership Questions 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.
Can you discuss your experience with version control systems like Git?
Can you discuss your experience with version control systems like Git?
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?
Provide an example of how you handled a disagreement with a teammate during a project.
Provide an example of how you handled a disagreement with a teammate during a project.
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 feedback from peers or supervisors?
How do you handle feedback from peers or supervisors?
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 lead a project and the outcome.
Describe a time when you had to lead a project and the outcome.
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 to excel as a software engineer?
What motivates you to excel as a software engineer?
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 promote collaboration within your team?
How do you promote collaboration within your 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?
- 01
Can you discuss your experience with version control systems like Git?
- 02
Provide an example of how you handled a disagreement with a teammate during a project.
- 03
How do you handle feedback from peers or supervisors?
- 04
Describe a time when you had to lead a project and the outcome.
How difficult are the interviews at HN Services Portugal?
The interviews can vary in difficulty, with technical assessments being particularly challenging. Candidates typically spend a few weeks preparing for coding and logic tests, so ensure you're well-practiced in these areas.
HN Services Portugal Software Engineer candidate reports ↗What differentiates successful candidates?
Successful candidates demonstrate a strong grasp of technical skills, but they also excel in communication and collaboration. Showing how you can work effectively within a team while contributing technically can set you apart.
HN Services Portugal Software Engineer candidate reports ↗What is the typical timeline from initial screening to offer?
The timeline can vary but generally spans 2-4 weeks. Candidates should expect prompt communication regarding next steps after interviews.
HN Services Portugal Software Engineer candidate reports ↗Can I work remotely or is it strictly in-office?
While many roles at HN Services Portugal may offer flexibility, it's best to clarify this during your interviews, as specific arrangements can depend on team needs.
HN Services Portugal Software Engineer candidate reports ↗How many rounds is the HN Services Portugal Software Engineer interview process?
Candidates report 2 stages: Initial Screening and Technical Assessments. The interview process section above breaks down what each stage covers.
HN Services Portugal Software Engineer candidate reports ↗What topics come up in the HN Services Portugal Software Engineer interview?
HN Services Portugal Software Engineer interviews most often cover Algorithmic problem solving, Logic testing (reasoning puzzles), Data structures & algorithms concepts, Sequence prediction, and SQL, based on topics extracted from real candidate reports.
HN Services Portugal 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.
- 01HN Services Portugal 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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