As a Software Engineer at KoBold Metals, you will play a pivotal role in shaping the future of sustainable mining technologies. This position is critical to the company's mission of leveraging advanced data analytics and machine learning to optimize mineral exploration. By integrating software solutions into the exploration process, you help the company reduce environmental impact while enhancing operational efficiency. In this role, you will work closely with cross-functional teams, including geologists, data scientists, and product managers, to develop software that supports innovative exploration methods. Your contributions will directly influence the effectiveness of our exploration projects, making this a unique opportunity to work at the intersection of technology and sustainability. Expect to engage with complex datasets, tackle challenging problems, and drive impactful solutions that align with KoBold Metals’ vision of a sustainable future.
Initial Introduction
reportedAn hour-long introduction with an engineering lead to discuss the role and company.
What to demonstrate
- An hour-long introduction with an engineering lead to discuss the role and company
- Depth in Architectural Design
How to prepare
- Answer aloud and timed: Explain the software development lifecycle and your experience with it.
- Answer aloud and timed: What programming languages are you most proficient in, and why?
Technical Evaluation
reportedThree one-hour interviews focused on assessing technical skills and problem-solving abilities.
What to demonstrate
- Three one-hour interviews focused on assessing technical skills and problem-solving abilities
- Depth in Architectural Design
How to prepare
- Answer aloud and timed: Describe how you would optimize a piece of code for performance.
- Answer aloud and timed: Can you discuss a challenging technical problem you faced and how you resolved it?
Behavioral Evaluation
reportedInterviews that evaluate soft skills and cultural fit within KoBold Metals.
What to demonstrate
- Interviews that evaluate soft skills and cultural fit within KoBold Metals
- Depth in Architectural Design
How to prepare
- Prepare three examples from your own work, each with a decision you made and an outcome you can quantify.
- Re-read the description of the behavioral evaluation above and write down what you would ask to confirm before it.
Executive Conversation
reportedA final discussion with an executive to assess overall fit and alignment with company values.
What to demonstrate
- A final discussion with an executive to assess overall fit and alignment with company values
- Depth in Architectural Design
How to prepare
- Answer aloud and timed: How would you approach designing an API for internal data consumption?
- Answer aloud and timed: Discuss how you would ensure scalability in a cloud-based application.
Take-Home Assignment
reportedCompletion of a take-home architectural design question, culminating in a technical design document.
What to demonstrate
- Completion of a take-home architectural design question, culminating in a technical design document
- Depth in Architectural Design
How to prepare
- Answer aloud and timed: What considerations would you make for system security in your designs?
- Answer aloud and timed: Describe a microservices architecture you have worked on.
PracHub editorial advice for the preparation topics above.
Align with the Company Mission
Understand the sustainability goals of KoBold Metals and be prepared to discuss how your work contributes to these objectives.
Practice Behavioral Questions
Use the STAR (Situation, Task, Action, Result) method to structure your responses, ensuring clarity and impact.
Showcase Your Projects
Be ready to discuss past projects that highlight your technical skills, problem-solving abilities, and teamwork.
Be Curious
Ask insightful questions during your interviews to demonstrate your interest in the role and the company.
Choose a category, try a prompt, then open its approach, worked solution or follow-up when you need it.
Solve a coding problem using your preferred programming language.
Solve a coding problem using your preferred programming language.
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 difference between a stack and a queue, and provide examples of their use cases.
Explain the difference 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?
Implement a function to reverse a linked list.
Implement 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?
Discuss the time complexity of your solution to a problem you solved.
Discuss the time complexity of your solution to a problem you solved.
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 do you approach learning new algorithms or data structures?
How do you approach learning new algorithms or data structures?
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?
Stop tag and share joins from fanning out a page
resource_tag is (resource_id, tag_id) with PK (resource_id, tag_id); resource_share is (resource_id, shared_with_user_id, permission). The tagged-and-shared listing inner-joins resource to both, filters tenant_id, tag_id = ANY($2) and shared_with_user_id = $3, orders by updated_at DESC and takes 50. Pages come back with fewer than 50 distinct resources and the total in the header is far too high. Explain the row multiplication, rewrite both the page query and the count query so each is correct, and name the index each one needs. PostgreSQL 16.
Approach
- Do the arithmetic against the predicates that are actually there. An inner join emits one row per matching child row, and both joins are filtered: tag_id = ANY($2) admits only the requested tags, shared_with_user_id = $3 admits one user's share rows. So a resource holding three of the requested tags and shared with $3 once yields three rows, not one — the multiplier is its count of matching tags times its share rows for that single user, and that second factor is 1 unless the table admits duplicate (resource_id, shared_with_user_id) pairs. LIMIT 50 then limits rows rather than resources, and COUNT(*) counts pairs — the header is the product, not the population.
- Reject DISTINCT as the fix. It deduplicates after the product has been built, so the planner must materialise and sort the fanned-out set before the LIMIT can apply, and it leaves any SUM or AVG in the same select list wrong.
- Rewrite both filters as semi-joins, keeping resource as the only row source: AND EXISTS (SELECT 1 FROM resource_tag rt WHERE rt.resource_id = r.resource_id AND rt.tag_id = ANY($2)) and the same shape against resource_share. A semi-join stops at the first match per resource and preserves the driving index order, so ORDER BY updated_at DESC, resource_id DESC LIMIT 50 still stops after 50 rows.
- Count with the same predicates and no join at all: SELECT count(*) FROM resource r WHERE r.tenant_id = $1 AND r.status = 'active' AND EXISTS (...) AND EXISTS (...). Nothing multiplies a resource, so the number is the population.
Follow-up
- The filter changes from 'any of these tags' to 'all of these tags'. Rewrite it and state what it costs relative to the ANY form.
- A resource can be shared with the same user twice under different permissions. Does your count change, and should it?
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?
What programming languages are you most proficient in, and why?
What programming languages are you most proficient in, 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?
Describe how you would optimize a piece of code for performance.
Describe how you would optimize a piece of code for performance.
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 discuss a challenging technical problem you faced and how you resolved it?
Can you discuss 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?
Explain a recent project where you implemented a new technology or tool.
Explain a recent project where you implemented a new technology or tool.
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?
Design a system that handles real-time data processing for mineral exploration.
Design a system that handles real-time data processing for mineral exploration.
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?
How would you approach designing an API for internal data consumption?
How would you approach designing an API for internal data consumption?
Approach
- Say who the caller is and what they do when the call fails halfway.
- Define the identity of a request so a retry cannot double-apply it.
- Separate accepted, pending, failed and confirmed; they are different facts.
- Design the error taxonomy before the success shape; callers branch on it.
Follow-up
- What happens if the caller retries after a timeout?
- How does a client discover it is on an old version of this contract?
Discuss how you would ensure scalability in a cloud-based application.
Discuss how you would ensure scalability in a cloud-based application.
Approach
- Fix the scope first: who calls this, how often, and what they do when it fails.
- Name the read and write paths separately; they rarely have the same bottleneck.
- Choose a partition key and say what query it makes expensive.
- State the consistency you need, and where you are willing to be stale.
Follow-up
- What breaks first when traffic grows ten times?
- How does this behave when that dependency is down for an hour?
What considerations would you make for system security in your designs?
What considerations would you make for system security in your designs?
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?
Describe a microservices architecture you have worked on.
Describe a microservices architecture you have worked on.
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?
You are given a dataset with missing values; how would you handle it?
You are given a dataset with missing values; how would you handle 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 would you approach a new problem that you've never encountered before?
How would you approach a new problem that you've never encountered before?
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 would evaluate the performance of a software application post-launch.
Describe how you would evaluate the performance of a software application post-launch.
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?
Present a case where you had to troubleshoot a production issue and the steps you took.
Present a case where you had to troubleshoot a production issue and the steps you took.
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?
Explain your thought process when debugging a complex issue.
Explain your thought process when debugging a complex issue.
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 KoBold Metals candidates report.
Prepare, practise & reflect
One practical outcome each day. Spend longer where you need it.
0 / 7 done01Map the KoBold Metals loop
- Write out the reported sequence: Initial Introduction, Technical Evaluation, Behavioral Evaluation, Executive Conversation, Take-Home Assignment.
- 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.
02Work Architectural Design
- Spend the session on Architectural Design, which KoBold Metals candidates report being tested on.
- Write one worked example in Architectural Design and time yourself on it.
Deliverable: One timed worked example in Architectural Design.
03Work Python
- Spend the session on Python, which KoBold Metals candidates report being tested on.
- Write one worked example in Python and time yourself on it.
Deliverable: One timed worked example in Python.
04Work Scientific Computing
- Spend the session on Scientific Computing, which KoBold Metals candidates report being tested on.
- Write one worked example in Scientific Computing and time yourself on it.
Deliverable: One timed worked example in Scientific Computing.
05Answer out loud: Technical / Domain Questions
- Answer aloud, timed: Explain the software development lifecycle and your experience with it.
- Answer aloud, timed: What programming languages are you most proficient in, and why?
Deliverable: Spoken answers to 2 reported Technical / Domain Questions question(s), under time.
06Answer out loud: System Design / Architecture
- Answer aloud, timed: Design a system that handles real-time data processing for mineral exploration.
- Answer aloud, timed: How would you approach designing an API for internal data consumption?
Deliverable: Spoken answers to 2 reported System Design / Architecture question(s), under time.
07Answer out loud: Behavioral / Leadership
- Answer aloud, timed: Describe a time when you had to lead a team through a challenging project.
- Answer aloud, timed: How do you handle conflicts in a team setting?
Deliverable: Spoken answers to 2 reported Behavioral / Leadership 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.
Explain the software development lifecycle and your experience with it.
Explain the software development lifecycle and your experience with it.
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 team through a challenging project.
Describe a time when you had to lead a team through a challenging 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 conflicts in a team setting?
How do you handle conflicts in a team setting?
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 give an example of how you effectively communicated a technical concept to a non-technical audience?
Can you give an example of how you effectively communicated a technical concept to a non-technical audience?
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?
Discuss a time when you took initiative to improve a process.
Discuss a time when you took initiative to improve a process.
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 managing multiple projects?
How do you prioritize tasks when managing multiple projects?
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
Explain the software development lifecycle and your experience with it.
- 02
Describe a time when you had to lead a team through a challenging project.
- 03
How do you handle conflicts in a team setting?
- 04
Can you give an example of how you effectively communicated a technical concept to a non-technical audience?
How difficult are the interviews at KoBold Metals?
The interviews are designed to be rigorous but fair, focusing on both technical skills and cultural fit. Candidates typically report feeling adequately prepared through thorough study and practice.
KoBold Metals Software Engineer candidate reports ↗What differentiates successful candidates?
Successful candidates demonstrate strong technical abilities, effective communication, and a clear alignment with the company's values and mission. They are also proactive in problem-solving and collaboration.
KoBold Metals Software Engineer candidate reports ↗What is the culture like at KoBold Metals?
The culture at KoBold Metals is collaborative and innovative, emphasizing teamwork and a shared mission of sustainability. Employees are encouraged to contribute ideas and take initiative in their roles.
KoBold Metals Software Engineer candidate reports ↗What is the typical timeline from initial screen to offer?
The interview process can take a few weeks, depending on scheduling and the number of candidates. It's advisable to remain patient and engaged throughout the process.
KoBold Metals Software Engineer candidate reports ↗Are there remote work options available?
While specific policies may vary by team, KoBold Metals generally supports flexible work arrangements, including hybrid models, depending on project needs.
KoBold Metals Software Engineer candidate reports ↗What topics does KoBold Metals test in interviews?
KoBold Metals interviews most often cover Python, Data Science (General), Architectural Design, Machine Learning (ML), and Data Analyst role expectations. The exact emphasis depends on the specific role you apply for.
KoBold Metals 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.
- 01KoBold Metals 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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