A Software Engineer at Lean Solutions Group plays a pivotal role in bridging the gap between top-tier Latin American talent and fast-growing businesses in the United States. As a premier nearshore services provider, the company embeds its engineers directly into client teams across diverse industries, including logistics, supply chain, healthcare, and SaaS. In this role, you are not just writing code; you are acting as a strategic partner, helping international clients scale their digital products, optimize complex workflows, and modernize legacy infrastructure. The impact of this position is immediate and highly visible. Whether you are hired as a Senior Backend Developer or a Senior Fullstack Developer, you will be responsible for designing, building, and maintaining robust, scalable systems that handle high transaction volumes and critical business data. Because you will be integrated into client-facing environments, your ability to write clean, maintainable code must be matched by your capacity to communicate technical concepts clearly to stakeholders who rely on your expertise. You will work within highly collaborative, agile environments where your technical decisions directly influence product roadmaps. For engineers who thrive on solving real-world business challenges, optimizing application performance, and working in cross-border teams, this position offers an unparalleled platform for professional growth and global exposure.
HR Screening
reportedReview of your resume, verification of English fluency, and discussion of career expectations.
What to demonstrate
- Review of your resume, verification of English fluency, and discussion of career expectations
- Depth in Java
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.
Psychological Evaluation
reportedAssessment of cognitive abilities, work style, and adaptability as part of the hiring process.
What to demonstrate
- Assessment of cognitive abilities, work style, and adaptability as part of the hiring process
- Depth in Java
How to prepare
- Answer aloud and timed: Explain the Spring Boot bean lifecycle and how dependency injection is managed under the hood.
- Answer aloud and timed: What are the best practices for exception handling in a RESTful API? How do you ensure meaningful error responses for clients?
Technical Evaluation
reportedDeep-dive questions on your core stack and coding exercises conducted by the internal engineering team.
What to demonstrate
- Deep-dive questions on your core stack and coding exercises conducted by the internal engineering team
- Depth in Java
How to prepare
- Answer aloud and timed: How do you optimize database queries in Spring Data JPA to avoid the N+1 select problem?
- Answer aloud and timed: Write an efficient algorithm to find the first non-repeated character in a given string.
Client Interview
reportedPresentation of your experience and technical capabilities directly to the US-based team.
What to demonstrate
- Presentation of your experience and technical capabilities directly to the US-based team
- Depth in Java
How to prepare
- Answer aloud and timed: Given an array of integers, write a function that moves all zeros to the end of the array while maintaining the relative order of the non-zero elements.
- Answer aloud and timed: How would you detect a cycle in a singly linked list? Explain the time and space complexity of your approach.
PracHub editorial advice for the preparation topics above.
Treat the internal team as your advocates
The internal recruiters and technical interviewers want you to succeed. If you perform well during the internal technical round, they will actively pitch you to their best clients and help prepare you for the client-specific interview.
Over-communicate during coding tests
When solving coding challenges, do not sit in silence. Explain your approach before you start typing, discuss any trade-offs you are making, and state how you plan to optimize the code. This shows how you collaborate under pressure.
Treat the internal technical interview as your gateway
The internal team needs to feel 100% confident in your skills before they present you to their premium US clients.
Choose a category, try a prompt, then open its approach, worked solution or follow-up when you need it.
How does multi-threading work in Java, and how do you prevent race conditions in a high-concurrency environmen
How does multi-threading work in Java, and how do you prevent race conditions in a high-concurrency environment?
Approach
- Say what the runtime actually does before reasoning about the code.
- Name what is shared across threads and what owns each piece of state.
- Identify the window where an invariant is briefly untrue.
- Distinguish a value from a reference to it, and say which one you handed out.
Follow-up
- What happens if two callers reach this at the same time?
- Where could this allocate more than you expect?
Write an efficient algorithm to find the first non-repeated character in a given string.
Write an efficient algorithm to find the first non-repeated character in a given 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?
Given an array of integers, write a function that moves all zeros to the end of the array while maintaining th
Given an array of integers, write a function that moves all zeros to the end of the array while maintaining the relative order of the non-zero elements.
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 detect a cycle in a singly linked list? Explain the time and space complexity of your approach.
How would you detect a cycle in a singly linked list? Explain the time and space complexity of your approach.
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?
Write a program to reverse a string without using built-in reverse functions.
Write a program to reverse a string without using built-in reverse functions.
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 an array of strings, write a method to group anagrams together.
Given an array of strings, write a method to group anagrams together.
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?
Replace offset paging on the resource feed with keyset
resource holds resource_id, tenant_id, owner_user_id, title, body_ref, version, status ('draft','active','archived','deleted'), created_at, updated_at, deleted_at, with an index on (tenant_id, status, updated_at DESC, resource_id DESC). The listing endpoint returns active resources for one tenant, newest update first, 50 per page, today with LIMIT 50 OFFSET n. Tenants reach page 400 and rows are created while they read. Write the keyset query, define what the cursor carries and how it is encoded, and say which part of the index each predicate uses. Assume PostgreSQL 16.
Approach
- Name the two failures separately. OFFSET 20000 makes the server produce and discard 20,000 rows, so page cost grows with depth rather than with page size. Independently, any write that changes how many rows sort above the offset moves the window between two fetches, and the direction decides which anomaly you get: an insert lands at the head of updated_at DESC and pushes already-returned rows down past the boundary, so they are returned a second time; a delete above the offset, or a row whose updated_at is bumped above the cursor, pulls rows up and one is never returned at all. Nothing in the response reveals either.
- Write the seek: WHERE tenant_id = $1 AND status = 'active' AND (updated_at, resource_id) < ($2, $3) ORDER BY updated_at DESC, resource_id DESC LIMIT 50. The row-value comparison is one index range rather than a disjunction, and both columns are NOT NULL, which is what makes that comparison well defined.
- Map each predicate onto the index: tenant_id and status are equality on the leading columns, (updated_at, resource_id) is the range, and the ORDER BY matches the index order so no Sort node appears and the scan stops after 50 rows. The DESC in the definition only matters for mixed directions — a plain ascending btree on the same columns is read backwards for this query.
- Put both sort columns in the cursor and nothing the client can tamper with into another tenant: base64 of (updated_at, resource_id), validated server-side, with tenant_id taken from the principal.
Follow-up
- The client asks for 'jump to page 400'. What do you offer instead, and what does the honest version cost?
- Sort order becomes user-selectable across four columns. How many indexes is that, and which would you refuse to add?
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?
Explain the difference between optimistic and pessimistic locking in database transactions, and when you would
Explain the difference between optimistic and pessimistic locking in database transactions, and when you would use each.
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 the Spring Boot bean lifecycle and how dependency injection is managed under the hood.
Explain the Spring Boot bean lifecycle and how dependency injection is managed under the hood.
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 best practices for exception handling in a RESTful API? How do you ensure meaningful error respon
What are the best practices for exception handling in a RESTful API? How do you ensure meaningful error responses for clients?
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?
How do you optimize database queries in Spring Data JPA to avoid the N+1 select problem?
How do you optimize database queries in Spring Data JPA to avoid the N+1 select problem?
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 solved in a past project. What were the trade-offs of your approa
Describe a challenging technical problem you solved in a past project. What were the trade-offs of your approach?
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 architecture of the most complex application you have designed or maintained?
Can you explain the architecture of the most complex application you have designed or maintained?
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 do you manage technical debt when working under tight client deadlines?
How do you manage technical debt when working under tight client deadlines?
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?
One customer endpoint stalls deliveries to every other destination
The egress service delivers about 1.5k webhooks/second across 40,000 destinations, with a per-destination concurrency cap of 4 and a 10-second connect-plus-read timeout. Throughput falls to 300/second, queue depth climbs, and p99 delivery latency for unaffected destinations goes from 200 ms to minutes, while the error rate barely moves. One tenant holds 900 destination rows whose URLs share a hostname that now answers in 9.5 seconds. Explain the mechanism with the arithmetic, then give the containment in the order you would apply it.
Approach
- Look at saturation before errors. A flat error rate with collapsing throughput says nothing is failing, things are waiting, so the first signal to pull is in-flight request count or pool wait time rather than the error counter. This is the distinction that decides the whole investigation.
- Group in-flight work by resolved host, not by destination id. The cap is keyed per destination row, so 900 rows sharing one hostname buy 3,600 concurrent slots against a single host, each held for 9.5 seconds. The bulkhead was never a bulkhead for that host, and grouping by the wrong dimension is why the dashboard looked healthy.
- Do the arithmetic in both directions. Required concurrency is arrival rate times latency, so 1.5k/second at 200 ms needs about 300 in flight, which is entirely consumed by 3,600 slow slots; conversely whatever concurrency is left sustains rate equals concurrency divided by 9.5 seconds, which is the 300/second you are seeing. Matching both numbers is what promotes this from a plausible story to the mechanism.
- Explain why the circuit breaker never helped. It opens on consecutive failures, and a 9.5-second response inside a 10-second timeout is a success. Slow is not failing, so an error-rate breaker cannot see this; you need a slow-call ratio, a deadline propagated from the caller's remaining budget, or a concurrency limiter.
Follow-up
- The host recovers to 80 ms. How long does the queue take to drain, and what does the drain do to the recovered host?
- Where should the 10-second timeout number actually come from?
Built from the rounds and topics Lean Solutions Group candidates report.
Prepare, practise & reflect
One practical outcome each day. Spend longer where you need it.
0 / 7 done01Map the Lean Solutions Group loop
- Write out the reported sequence: HR Screening, Psychological Evaluation, Technical Evaluation, Client 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 Java
- Spend the session on Java, which Lean Solutions Group candidates report being tested on.
- Write one worked example in Java and time yourself on it.
Deliverable: One timed worked example in Java.
03Work Spring Boot
- Spend the session on Spring Boot, which Lean Solutions Group candidates report being tested on.
- Write one worked example in Spring Boot and time yourself on it.
Deliverable: One timed worked example in Spring Boot.
04Work Backend Development
- Spend the session on Backend Development, which Lean Solutions Group candidates report being tested on.
- Write one worked example in Backend Development and time yourself on it.
Deliverable: One timed worked example in Backend Development.
05Answer out loud: Core Backend & Frameworks
- Answer aloud, timed: Explain the difference between optimistic and pessimistic locking in database transactions, and when you would use each.
- Answer aloud, timed: How does multi-threading work in Java, and how do you prevent race conditions in a high-concurrency environment?
Deliverable: Spoken answers to 2 reported Core Backend & Frameworks question(s), under time.
06Answer out loud: Coding & Algorithmic Problem Solving
- Answer aloud, timed: Write an efficient algorithm to find the first non-repeated character in a given string.
- Answer aloud, timed: Given an array of integers, write a function that moves all zeros to the end of the array while maintaining the relative order of the non-zero elements.
Deliverable: Spoken answers to 2 reported Coding & Algorithmic Problem Solving question(s), under time.
07Answer out loud: Experience & Client-Facing Scenarios
- Answer aloud, timed: Describe a challenging technical problem you solved in a past project. What were the trade-offs of your approach?
- Answer aloud, timed: How do you handle a situation where a client requests a feature that negatively impacts system performance or security?
Deliverable: Spoken answers to 2 reported Experience & Client-Facing Scenarios 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.
How do you handle a situation where a client requests a feature that negatively impacts system performance or
How do you handle a situation where a client requests a feature that negatively impacts system performance or security?
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 your experience working with agile methodologies in a distributed team environment.
Describe your experience working with agile methodologies in a distributed team environment.
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?
Narrate an outage you owned from page to postmortem
Pick an incident you personally drove, ideally one where writes were affected rather than reads. In six to eight minutes: state the symptom as it first appeared on a dashboard, the blast radius you established before you knew the cause, the mitigation you applied and when, the mechanism you eventually proved, and the follow-up that would prevent a repeat. Bring numbers: error rate, tenants affected, minutes to mitigate, minutes to resolve. If you cannot name what you measured, choose a different incident.
Approach
- Open on the signal rather than the cause: which metric at which percentile moved, on which service, at what time, so the listener follows the same evidence you had rather than a conclusion you already reached.
- Separate mitigation from diagnosis out loud. State what you did to stop the bleeding (flag off, shed traffic, drain a lease, roll back a deploy) and say plainly that you did it before the mechanism was known, because those are two jobs with different deadlines.
- Establish blast radius in countable terms: how many tenants, how many writes, and crucially whether the effect was loss or only delay. An append-only revision table or a pending outbox row means the change survived and the projection was merely behind, which is a repair rather than a data-loss incident.
- Prove the mechanism instead of asserting it. Name the trace span that grew, the plan that flipped to a sequential scan, the lease that expired, plus one alternative you ruled out and the signal that stayed flat while you ruled it out.
Follow-up
- What would you do differently in the first five minutes, given the same dashboard and no more information?
- Which follow-up action did you deliberately not take, and why was dropping it the right call?
- 01
How do you handle a situation where a client requests a feature that negatively impacts system performance or security?
- 02
Describe your experience working with agile methodologies in a distributed team environment.
- 03
Pick an incident you personally drove, ideally one where writes were affected rather than reads. In six to eight minutes: state the symptom as it first appeared on a dashboard, the blast radius you established before you knew the cause, the mitigation you applied and when, the mechanism you eventually proved, and the follow-up that would prevent a repeat. Bring numbers: error rate, tenants affected, minutes to mitigate, minutes to resolve. If you cannot name what you measured, choose a different incident.
How long does the entire interview process take from start to finish?
The process typically takes between two to four weeks. The internal stages (HR screen, psychological test, and internal technical round) usually move quite fast. The final client interview timing depends entirely on the availability of the specific US client matching your profile.
Lean Solutions Group Software Engineer candidate reports ↗Why does Lean Solutions Group require a psychological evaluation?
This is a standard evaluation step in many Latin American corporate environments. It is designed to assess your cognitive processing, workplace behavior, stress management, and cultural adaptability. It helps ensure that you will thrive in a fast-paced, client-facing consulting environment.
Lean Solutions Group Software Engineer candidate reports ↗What is the format of the technical interview?
The internal technical interview is a mix of theoretical questions covering your primary tech stack (such as Java, Spring Boot, and database concepts) and live coding exercises. The coding exercises generally focus on string and array manipulations, where you are expected to write clean code and explain your logic.
Lean Solutions Group Software Engineer candidate reports ↗Do I need to have perfect English to get hired?
You do not need a perfect accent, but you must have a strong professional command of the language (typically B2 or C1 level). You must be able to confidently explain complex technical concepts, participate in client discussions, and write clear documentation without communication barriers.
Lean Solutions Group Software Engineer candidate reports ↗Is this position fully remote, hybrid, or on-site?
This depends on the specific client contract and your location. Lean Solutions Group has physical offices in cities like Medellín, but many of their software engineering roles offer highly flexible remote or hybrid work arrangements. Your recruiter will clarify the specific setup during your initial screening.
Lean Solutions Group Software Engineer candidate reports ↗What topics does Lean Solutions Group test in interviews?
Lean Solutions Group interviews most often cover Java, Requirements Elicitation, Requirements Analysis, Spring Boot, and Backend Development. The exact emphasis depends on the specific role you apply for.
Lean Solutions Group 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.
- 01Lean Solutions Group 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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