A Software Engineer at Four Hands plays a pivotal role in designing and developing innovative software solutions that enhance the user experience and drive business growth. This position is crucial as it directly influences the quality and performance of the company's products, ultimately impacting customer satisfaction and loyalty. As a Software Engineer, you will work on a variety of projects, from developing backend systems that support core functionalities to creating user-facing applications that engage customers. At Four Hands, software engineers are not just coders; they are problem solvers who collaborate with cross-functional teams to create scalable solutions. You will be involved in various stages of the software development lifecycle, including requirements gathering, design, implementation, testing, and deployment. This role offers the opportunity to work on complex systems and contribute to strategic initiatives that shape the future of the company, making it both exciting and rewarding.
Initial Screening Call
reportedFirst contact to evaluate candidate's background and fit for the role.
What to demonstrate
- First contact to evaluate candidate's background and fit for the role
- Depth in EDI Development
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 Discussions
reportedEngagement in technical discussions to assess problem-solving skills.
What to demonstrate
- Engagement in technical discussions to assess problem-solving skills
- Depth in EDI Development
How to prepare
- Answer aloud and timed: How do you approach debugging issues in your code?
- Answer aloud and timed: How would you design a system to handle millions of concurrent users?
Behavioral Interviews
reportedInterviews focused on understanding cultural fit and candidate's thought process.
What to demonstrate
- Interviews focused on understanding cultural fit and candidate's thought process
- Depth in EDI Development
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 interviews above and write down what you would ask to confirm before it.
Final Evaluations
reportedLast stage of the interview process to make final assessments before decisions.
What to demonstrate
- Last stage of the interview process to make final assessments before decisions
- Depth in EDI Development
How to prepare
- Answer aloud and timed: Tell me about a time you had to work with a difficult team member.
- Answer aloud and timed: How do you prioritize your tasks when you have multiple deadlines?
PracHub editorial advice for the preparation topics above.
Understand the Company Values
Familiarize yourself with Four Hands' mission and values. This knowledge will help you articulate how you align with the company during your interviews.
Practice Behavioral Questions
Prepare for behavioral questions by using the STAR method (Situation, Task, Action, Result) to frame your responses.
Be Ready to Discuss Projects
Have a few key projects in mind that you can discuss in detail, highlighting your contributions and the impact of your work.
Engage with Interviewers
Treat interviews as a two-way conversation. Ask insightful questions to demonstrate your interest and engagement with the role and the company.
Choose a category, try a prompt, then open its approach, worked solution or follow-up when you need it.
Walk me through your thought process in solving a complex algorithm problem.
Walk me through your thought process in solving a complex algorithm problem.
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 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?
How would you implement a binary search algorithm?
How would you implement a binary search algorithm?
Approach
- Restate the input: its shape, its size, and what is guaranteed about it.
- Name the brute-force solution and its complexity before improving on it.
- Choose the data structure from the access pattern, not from familiarity.
- State the target complexity and say which constraint rules the naive version out.
Follow-up
- How does this change if the input no longer fits in memory?
- What is the worst case, and how likely is it on real data?
Can you explain the time complexity of your solution?
Can you explain the time complexity of your solution?
Approach
- Restate the input: its shape, its size, and what is guaranteed about it.
- Name the brute-force solution and its complexity before improving on it.
- Choose the data structure from the access pattern, not from familiarity.
- State the target complexity and say which constraint rules the naive version out.
Follow-up
- How does this change if the input no longer fits in memory?
- What is the worst case, and how likely is it on real data?
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?
Denormalise tenant onto revisions and backfill it live
resource_revision (revision_id, resource_id, version, actor_user_id, change_kind, patch, request_id, created_at) has 400M rows and no tenant column; tenant_id lives only on resource. Two reads need it: a tenant-scoped audit feed ordered by created_at DESC, and an offboarding purge. Both join back to resource today. Justify adding tenant_id to resource_revision against those two reads, name the anomaly the copy introduces and the constraint that prevents it, then give the ordered migration for a live table taking 1.2k writes/second — the lock each step takes, how the backfill is batched, and where each step stops being reversible. PostgreSQL 16.
Approach
- Justify from the access path rather than from taste. Without the column, the audit feed either scans resource_revision by created_at and discards other tenants' rows, or resolves the tenant's resource_ids first and probes with them — both proportional to the tenant's whole history rather than to one page. With (tenant_id, created_at DESC, revision_id DESC) it is a seek that stops at 50 rows, and the purge becomes a ranged delete instead of a join.
- Name the cost exactly: a second copy of a fact can disagree with the first. Make the disagreement unwritable rather than documented — add UNIQUE (resource_id, tenant_id) on resource so it can serve as a foreign-key target, then FOREIGN KEY (resource_id, tenant_id) REFERENCES resource (resource_id, tenant_id) on the revision table. A revision can then only ever carry its parent's tenant.
- Step one, expand: ALTER TABLE resource_revision ADD COLUMN tenant_id BIGINT NULL, with no default, so it is a catalogue change and no rewrite. It still needs ACCESS EXCLUSIVE for an instant, and that instant queues behind the longest open transaction on the table while every later query queues behind it — set lock_timeout to 2s and retry rather than wait.
- Step two, dual-write: deploy the writer that populates tenant_id on every new revision while reads still use the join. Reversible by redeploying the previous build, because nothing reads the column yet.
Follow-up
- The backfill is half finished and a rollback is required. What state is the table in, and what does the previous build do with a half-populated column?
- How do you verify the backfill actually finished, given rows are still being inserted while it runs?
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 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 would you design a system to handle millions of concurrent users?
How would you design a system to handle millions of concurrent users?
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 the trade-offs you consider when choosing between different architectural patterns.
Describe the trade-offs you consider when choosing between different architectural patterns.
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?
Can you explain how you would optimize a database for performance?
Can you explain how you would optimize a database for performance?
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?
Given a scenario where a critical application is down, how would you handle the situation?
Given a scenario where a critical application is down, how would you handle the situation?
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 developing a solution for a customer-facing feature?
How do you approach developing a solution for a customer-facing feature?
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 issues in your code?
How do you approach debugging issues 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 Four Hands candidates report.
Prepare, practise & reflect
One practical outcome each day. Spend longer where you need it.
0 / 7 done01Map the Four Hands loop
- Write out the reported sequence: Initial Screening Call, Technical Discussions, Behavioral Interviews, Final Evaluations.
- 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 EDI Development
- Spend the session on EDI Development, which Four Hands candidates report being tested on.
- Write one worked example in EDI Development and time yourself on it.
Deliverable: One timed worked example in EDI Development.
03Work Salesforce Development
- Spend the session on Salesforce Development, which Four Hands candidates report being tested on.
- Write one worked example in Salesforce Development and time yourself on it.
Deliverable: One timed worked example in Salesforce Development.
04Work Software Engineering
- Spend the session on Software Engineering, which Four Hands candidates report being tested on.
- Write one worked example in Software Engineering and time yourself on it.
Deliverable: One timed worked example in Software Engineering.
05Answer out loud: Technical / Domain Questions
- Answer aloud, timed: What programming languages are you most proficient in, and why?
- Answer aloud, timed: Describe a challenging technical problem you faced and how you resolved it.
Deliverable: Spoken answers to 2 reported Technical / Domain Questions question(s), under time.
06Answer out loud: System Design / Architecture
- Answer aloud, timed: How would you design a system to handle millions of concurrent users?
- Answer aloud, timed: Describe the trade-offs you consider when choosing between different architectural patterns.
Deliverable: Spoken answers to 2 reported System Design / Architecture question(s), under time.
07Answer out loud: Behavioral / Leadership
- Answer aloud, timed: Tell me about a time you had to work with a difficult team member.
- Answer aloud, timed: How do you prioritize your tasks when you have multiple deadlines?
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.
Tell me about a time you had to work with a difficult team member.
Tell me about a time you had to work with a difficult team member.
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 your tasks when you have multiple deadlines?
How do you prioritize your tasks when you have multiple deadlines?
Approach
- Pick a story where you made the decision, not one where you watched it.
- State the situation in two sentences and spend the rest on the reasoning.
- Give the blast radius: what could have broken, and what you measured.
- Name the disagreement and how you resolved it with evidence.
Follow-up
- What would you do differently if you ran that again?
- How did you know your change caused the improvement?
What motivates you in your work as a software engineer?
What motivates you in your work 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?
- 01
Tell me about a time you had to work with a difficult team member.
- 02
How do you prioritize your tasks when you have multiple deadlines?
- 03
What motivates you in your work as a software engineer?
How difficult are the interviews, and how much preparation time is typical?
Interviews at Four Hands can range from average to difficult, depending on the specific role and team. Candidates typically spend a few weeks preparing, focusing on technical skills as well as behavioral questions.
Four Hands Software Engineer candidate reports ↗What differentiates successful candidates?
Successful candidates often demonstrate a strong technical foundation, effective communication skills, and a collaborative mindset. They can articulate their thought processes clearly and provide examples that showcase their problem-solving abilities.
Four Hands Software Engineer candidate reports ↗What is the culture and working style like at Four Hands?
Four Hands fosters a collaborative and open culture where team members are encouraged to share ideas and feedback. The working style emphasizes flexibility and adaptability, allowing teams to pivot as project needs change.
Four Hands Software Engineer candidate reports ↗What is the typical timeline from initial screening to offer?
The timeline can vary, but candidates can expect a few weeks from the initial screening to the final offer, depending on the scheduling of interviews and the decision-making process.
Four Hands Software Engineer candidate reports ↗Are there remote work or hybrid expectations?
While specific arrangements may vary, Four Hands generally supports flexible working environments, including remote and hybrid options, depending on the team's needs and project requirements.
Four Hands Software Engineer candidate reports ↗What topics does Four Hands test in interviews?
Four Hands interviews most often cover Variance Analysis, Key Performance Indicators (KPIs), Project Management, UX/UI Design, and Demand Planning. The exact emphasis depends on the specific role you apply for.
Four Hands 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.
- 01Four Hands 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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