As a Software Engineer at Repsol México, you are at the intersection of traditional energy operations and cutting-edge digital transformation. Your role is pivotal in developing the systems that optimize complex industrial processes, manage large-scale data, and enhance the safety and efficiency of our global operations. You aren't just writing code; you are building the digital backbone that enables Repsol to innovate in a rapidly evolving energy landscape. The work is intellectually demanding and offers significant scope for impact. You will collaborate with multidisciplinary teams—ranging from data scientists and operations experts to fellow engineers—to solve problems that directly affect production, quality assurance, and environmental compliance. Whether you are working on internal tools or large-scale infrastructure, your contributions will have a tangible effect on how we deliver energy solutions to the world. ##### Tip Prepare to speak about the energy industry. Understanding the balance between technical excellence and operational safety is a key differentiator for candidates at Repsol.
High-Level Screening
reportedInitial assessment to evaluate candidate's basic qualifications and fit.
What to demonstrate
- Initial assessment to evaluate candidate's basic qualifications and fit
- Depth in English proficiency (business/technical)
How to prepare
- Answer aloud and timed: Describe a time you had to optimize a piece of code for performance or efficiency.
- Answer aloud and timed: How do you approach planning quality assurance and quality control procedures in a software project?
Online Assessments
reportedCandidates complete assessments testing logic, personality, and English proficiency.
What to demonstrate
- Candidates complete assessments testing logic, personality, and English proficiency
- Depth in English proficiency (business/technical)
How to prepare
- Answer aloud and timed: Explain your process for debugging a complex system failure in a production environment.
- Answer aloud and timed: Given a technical equipment manual, how would you translate those requirements into a functional software screen or table?
Remote Interviews
reportedInterviews with HR representatives and technical peers to assess skills and alignment.
What to demonstrate
- Interviews with HR representatives and technical peers to assess skills and alignment
- Depth in English proficiency (business/technical)
How to prepare
- Answer aloud and timed: How do you ensure your code remains maintainable and scalable as project requirements change?
- Answer aloud and timed: Why do you want to work for a company in the energy sector specifically?
Final Departmental Interview
reportedMeeting with the hiring manager or department head to finalize candidate evaluation.
What to demonstrate
- Meeting with the hiring manager or department head to finalize candidate evaluation
- Depth in English proficiency (business/technical)
How to prepare
- Answer aloud and timed: Tell me about a time you had to navigate a disagreement with a team member or stakeholder.
- Answer aloud and timed: How do you prioritize tasks when faced with multiple urgent requests?
PracHub editorial advice for the preparation topics above.
Prepare for Group Dynamics
You may be asked to solve a puzzle or case study with other candidates. Focus on being a collaborative leader rather than just the loudest voice in the room.
Study the Industry
Understanding the current challenges in the energy and oil & gas sectors will set you apart from candidates who only focus on the technical side.
Be Ready for "Rapid-Fire" Questions
Some interviewers use a fast-paced questioning style to see how you think on your feet. Stay calm and answer concisely.
Follow Up Professionally
If there is a delay in communication, a polite follow-up email is perfectly acceptable and shows your continued interest in the position.
Choose a category, try a prompt, then open its approach, worked solution or follow-up when you need it.
Find overlapping job attempts and peak concurrency from lease records
A day of job_run history yields about 50,000,000 attempt records: (job_run_id, job_type, attempt, started_at, finished_at which is NULL when the worker died, lease_expires_at). Leases expire on a clock, so a job that outran its lease ran twice. Produce (a) every job_run_id whose attempts overlapped in wall-clock time and (b) the peak number of simultaneously running attempts per job_type with the minute it occurred. Target O(n log n). State how you treat a NULL finished_at and what clock skew does to your answer.
Approach
- Define the interval before sorting anything: an attempt occupies [started_at, COALESCE(finished_at, lease_expires_at)). finished_at is observed and lease_expires_at is only a promise, so every attempt without a finish contributes an estimate and the whole result is a lower bound on overlap rather than an exact count.
- For peak concurrency, sweep: emit 2n endpoints, sort by (timestamp, kind) with ends ordered before starts at equal timestamps, then walk the sequence maintaining a counter per job_type and record each type's maximum with its timestamp. O(n log n) dominated by the sort, O(n) space, or O(1) extra if the sort is external and the walk streams.
- For overlap detection, do not compare attempts pairwise. A single global sort by (job_run_id, started_at) gives both the grouping and the order; within a group, keep the maximum end seen so far and report an overlap exactly when the next start is less than that running maximum, which is one linear pass after the sort.
- Half-open intervals matter and are easy to get wrong: with closed intervals an attempt ending at the same millisecond another begins reads as concurrency two, and across 50,000,000 records that artefact swamps the real signal.
Follow-up
- A handler is not idempotent and you have found 400 overlapping jobs. Which of them actually caused damage, and what would you query to find out?
- Peak concurrency for one job_type is 4 against a configured cap of 4. Is the cap working, or is the data hiding attempts that never started?
Collapse a redelivered event batch into per-aggregate high-water marks
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
- 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.
- 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.
- 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.
- 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?
Canonicalise a request body into a stable idempotency fingerprint
idempotency_key.request_fingerprint is a SHA-256 over the method, path and canonicalised body, and a retry whose fingerprint differs must be rejected with 422 rather than served the stored response. Write the canonicaliser. Bodies are JSON up to 256 KB nested at most 32 levels; clients vary key order, whitespace and unicode escaping, and some send 64-bit ids as JSON numbers. Produce a deterministic byte string such that semantically identical bodies match and any semantic difference does not. State your complexity and name two normalisations you refuse to perform.
Approach
- Parse once into a tree, then re-serialise under fixed rules: object keys sorted, array order preserved, one escaping convention, no insignificant whitespace. Parsing is O(n) and sorting keys is O(k log k) per object, so O(n log n) overall with O(depth) stack, and the 32-level cap is enforced during parsing because hostile nesting is how a canonicaliser becomes a stack overflow.
- Sort keys by their UTF-8 bytes and say why the obvious implementation is wrong in some runtimes: a default string comparison that orders by UTF-16 code units places surrogate pairs, meaning code points from U+10000 up, below U+E000 to U+FFFF, which is not UTF-8 byte order, so two services written in different languages disagree on the same document.
- Do not re-encode numbers through a double. IEEE-754 binary64 represents integers exactly only up to 2^53, so normalising a 19-digit id through a float changes it, and 1 against 1.0 cannot be reconciled without deciding whether they are the same value. Preserve the literal token, and require ids as strings at the API boundary if you want them comparable.
- Reject duplicate keys rather than picking one. JSON permits them and parsers disagree, most keeping the last, so any choice you make ties the fingerprint to a parser detail that the code handling the request does not necessarily share.
Follow-up
- A client sends the same logical request with an extra field your API ignores. Same key, different fingerprint, so you return 422. Is that the right answer?
- Where does the fingerprint get computed relative to request decompression and the body-size limit?
Keep soft-deleted accounts from blocking re-registration
app_user holds user_id, tenant_id, email CITEXT, password_hash (NULL for SSO principals), email_verified_at, auth_version, status ('invited','active','suspended','deactivated'), created_at, updated_at, deleted_at. Two live accounts for one address inside a tenant must be impossible, but an address freed by a soft delete must be reusable, and the same tenant may delete and re-register it repeatedly. Write the uniqueness DDL for PostgreSQL 16, then the equivalent for MySQL 8 where partial indexes do not exist, and say what each permits once three deleted rows already hold that address.
Approach
- Start from what is actually unique: not (tenant_id, email), but (tenant_id, email) among live rows. PostgreSQL says that directly — CREATE UNIQUE INDEX app_user_live_email ON app_user (tenant_id, email) WHERE deleted_at IS NULL. A full constraint over the same two columns burns the address permanently the first time someone deletes an account.
- Keep case-insensitivity in the type or the index, never in the application: CITEXT as given, or UNIQUE (tenant_id, lower(email)) as an expression index where the extension is unavailable. A case-sensitive unique column is exactly how two accounts for one human appear.
- For MySQL 8 the predicate has to move inside the key: add a discriminator column that is a constant 0 while the row is live and is set to user_id on delete, with UNIQUE (tenant_id, email, deleted_marker). Live rows share the constant and still collide; deleted rows differ from each other and stop colliding.
- State the NULL variant and its dependency: leaving the marker NULL for deleted rows also works, because a unique index treats NULLs as distinct — true in MySQL, and true in PostgreSQL only under the default NULLS DISTINCT, which PostgreSQL 15 lets you reverse. Check the polarity against the three existing deleted rows: constant-on-live is what preserves the collision you want, and reversing it silently admits duplicate live accounts.
Follow-up
- A deleted account re-registers with the same address the next day. Do the old resource rows follow the new user_id, and how does the API keep the two principals apart?
- How do you honour an erasure request while resource_revision.actor_user_id still references this table?
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?
How do you approach planning quality assurance and quality control procedures in a software project?
How do you approach planning quality assurance and quality control procedures in a software 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?
Given a technical equipment manual, how would you translate those requirements into a functional software scre
Given a technical equipment manual, how would you translate those requirements into a functional software screen or table?
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 your code remains maintainable and scalable as project requirements change?
How do you ensure your code remains maintainable and scalable as project requirements change?
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?
Explain your process for debugging a complex system failure in a production environment.
Explain your process for debugging a complex system failure in a production environment.
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 Repsol México candidates report.
Prepare, practise & reflect
One practical outcome each day. Spend longer where you need it.
0 / 7 done01Map the Repsol México loop
- Write out the reported sequence: High-Level Screening, Online Assessments, Remote Interviews, Final Departmental Interview.
- 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 4 reported rounds, with the weakest marked.
02Work English proficiency (business/technical)
- Spend the session on English proficiency (business/technical), which Repsol México candidates report being tested on.
- Write one worked example in English proficiency (business/technical) and time yourself on it.
Deliverable: One timed worked example in English proficiency (business/technical).
03Work Communication skills
- Spend the session on Communication skills, which Repsol México 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.
04Work Technical interview readiness
- Spend the session on Technical interview readiness, which Repsol México candidates report being tested on.
- Write one worked example in Technical interview readiness and time yourself on it.
Deliverable: One timed worked example in Technical interview readiness.
05Answer out loud: Technical and Analytical Aptitude
- Answer aloud, timed: Describe a time you had to optimize a piece of code for performance or efficiency.
- Answer aloud, timed: How do you approach planning quality assurance and quality control procedures in a software project?
Deliverable: Spoken answers to 2 reported Technical and Analytical Aptitude question(s), under time.
06Answer out loud: Behavioral and Cultural Fit
- Answer aloud, timed: Why do you want to work for a company in the energy sector specifically?
- Answer aloud, timed: Tell me about a time you had to navigate a disagreement with a team member or stakeholder.
Deliverable: Spoken answers to 2 reported Behavioral and Cultural Fit question(s), under time.
07Dry run for Repsol México
- Run one full mock under time, then write down the two questions you most want to ask your interviewers.
Deliverable: A completed timed mock and two questions to ask.
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 time you had to optimize a piece of code for performance or efficiency.
Describe a time you had to optimize a piece of code for performance or efficiency.
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?
Why do you want to work for a company in the energy sector specifically?
Why do you want to work for a company in the energy sector specifically?
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?
Tell me about a time you had to navigate a disagreement with a team member or stakeholder.
Tell me about a time you had to navigate a disagreement with a team member or stakeholder.
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 urgent requests?
How do you prioritize tasks when faced with multiple urgent requests?
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 situation where you had to learn a new technology or tool under a tight deadline.
Describe a situation where you had to learn a new technology or tool under a tight deadline.
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 do you consider your greatest professional achievement, and how did it contribute to your team's goals?
What do you consider your greatest professional achievement, and how did it contribute to your team's goals?
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 time you had to optimize a piece of code for performance or efficiency.
- 02
Why do you want to work for a company in the energy sector specifically?
- 03
Tell me about a time you had to navigate a disagreement with a team member or stakeholder.
- 04
How do you prioritize tasks when faced with multiple urgent requests?
How long does the entire interview process take?
It can vary significantly, ranging from a few weeks to several months. The process is thorough, so patience and consistent follow-up are important traits to demonstrate.
Repsol México Software Engineer candidate reports ↗Are the technical tests very difficult?
They are designed to test your logical reasoning and fundamental technical skills. If you are comfortable with standard coding challenges and analytical logic tests, you should be well-prepared.
Repsol México Software Engineer candidate reports ↗What is the most important trait for a successful candidate?
Beyond technical skills, we look for "cultural fit"—the ability to work well within a large, global organization and a genuine interest in the energy sector.
Repsol México Software Engineer candidate reports ↗Will I be interviewed in English?
Yes, expect a portion of the process—including tests and potentially group interviews—to be conducted in English to ensure you can operate in our global environment.
Repsol México Software Engineer candidate reports ↗What topics does Repsol México test in interviews?
Repsol México interviews most often cover Power BI (Advanced), English proficiency (business/technical), Case Interviewing, Pricing Analytics, and Communication skills. The exact emphasis depends on the specific role you apply for.
Repsol México 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.
- 01Repsol México 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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