The role of a Software Engineer at ESS is pivotal in shaping the technological backbone of the company. As a Software Engineer, you will engage in the design, development, and implementation of software solutions that are integral to our innovative products. Your contributions will not only enhance user experience but also drive efficiency and reliability in our systems, making a tangible impact on our customers and business operations. In this role, you will collaborate with cross-functional teams, including product management, quality assurance, and operations, to deliver high-quality software that meets market demands. You will work on exciting projects that involve cutting-edge technologies, contributing to solutions that push the boundaries of what's possible. Expect to solve complex problems, tackle scalable design challenges, and influence the future direction of our software offerings, all while being part of a dynamic and forward-thinking environment.
Recruiter Call
reportedInitial screening call with a recruiter to discuss your background and fit for the role.
What to demonstrate
- Initial screening call with a recruiter to discuss your background and fit for the role
- Depth in Communication (technical interview)
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 Interviews
reportedOne or more technical interviews that may include coding assessments or system design discussions.
What to demonstrate
- One or more technical interviews that may include coding assessments or system design discussions
- Depth in Communication (technical interview)
How to prepare
- Answer aloud and timed: How do you ensure the code you write is maintainable and scalable?
- Answer aloud and timed: Describe a challenging technical problem you encountered and how you resolved it.
Behavioral Questions
reportedInterviews include behavioral questions to understand your past experiences and professional outlook.
What to demonstrate
- Interviews include behavioral questions to understand your past experiences and professional outlook
- Depth in Communication (technical interview)
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 questions above and write down what you would ask to confirm before it.
PracHub editorial advice for the preparation topics above.
Prepare Thoroughly
Familiarize yourself with the technologies and methodologies relevant to the role. Being well-prepared demonstrates your commitment and expertise.
Practice Problem Solving
Work through coding challenges on platforms like LeetCode or HackerRank to sharpen your skills.
Communicate Clearly
During interviews, articulate your thought process clearly. This not only shows your understanding but also helps interviewers follow your reasoning.
Align with Company Values
Research ESS's mission and values. Be ready to discuss how your personal and professional values align with the company's culture.
Choose a category, try a prompt, then open its approach, worked solution or follow-up when you need it.
Can you explain the differences between synchronous and asynchronous programming?
Can you explain the differences between synchronous and asynchronous programming?
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 a function to reverse a string. What is the time complexity?
Write a function to reverse a string. What is the time complexity?
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?
Solve a problem involving data structures, like arrays or linked lists.
Solve a problem involving data structures, like arrays or linked lists.
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 differences between depth-first and breadth-first search.
Explain the differences between depth-first and breadth-first search.
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 provide an example of a situation where you optimized code for performance?
Can you provide an example of a situation where you optimized code for performance?
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?
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 ensure the code you write is maintainable and scalable?
How do you ensure the code you write is maintainable and scalable?
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 challenging technical problem you encountered and how you resolved it.
Describe a challenging technical problem you encountered 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?
What programming languages are you most comfortable with, and why?
What programming languages are you most comfortable with, 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?
How would you design a system to handle a high volume of transactions?
How would you design a system to handle a high volume of transactions?
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 the concept of microservices and when to use them.
Explain the concept of microservices and when to use them.
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 take into account for database design in a large application?
What considerations would you take into account for database design in a large 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?
Describe how you would approach designing an API for a new feature.
Describe how you would approach designing an API for a new feature.
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?
What are some common pitfalls in system design that you have encountered?
What are some common pitfalls in system design that you have encountered?
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 dataset, describe how you would identify trends and insights.
Given a dataset, describe how you would identify trends and insights.
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?
Provide a solution for a scenario where the system performance is degrading.
Provide a solution for a scenario where the system performance is degrading.
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 evaluate the effectiveness of your solutions?
How do you evaluate the effectiveness of your solutions?
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 debugging a complex issue in a production environment?
How would you approach debugging a complex issue 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 ESS candidates report.
Prepare, practise & reflect
One practical outcome each day. Spend longer where you need it.
0 / 7 done01Map the ESS loop
- Write out the reported sequence: Recruiter Call, Technical Interviews, Behavioral Questions.
- 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 3 reported rounds, with the weakest marked.
02Work Communication (technical interview)
- Spend the session on Communication (technical interview), which ESS candidates report being tested on.
- Write one worked example in Communication (technical interview) and time yourself on it.
Deliverable: One timed worked example in Communication (technical interview).
03Work Reliability engineering
- Spend the session on Reliability engineering, which ESS candidates report being tested on.
- Write one worked example in Reliability engineering and time yourself on it.
Deliverable: One timed worked example in Reliability engineering.
04Work Data privacy & confidentiality (NDA awareness)
- Spend the session on Data privacy & confidentiality (NDA awareness), which ESS candidates report being tested on.
- Write one worked example in Data privacy & confidentiality (NDA awareness) and time yourself on it.
Deliverable: One timed worked example in Data privacy & confidentiality (NDA awareness).
05Answer out loud: Technical / Domain Questions
- Answer aloud, timed: What is your experience with version control systems, such as Git?
- Answer aloud, timed: Can you explain the differences between synchronous and asynchronous programming?
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 a high volume of transactions?
- Answer aloud, timed: Explain the concept of microservices and when to use them.
Deliverable: Spoken answers to 2 reported System Design / Architecture question(s), under time.
07Answer out loud: Behavioral / Leadership
- Answer aloud, timed: Describe a situation where you had to collaborate with a difficult team member.
- Answer aloud, timed: How do you prioritize 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.
What is your experience with version control systems, such as Git?
What is your experience with version control systems, such as Git?
Approach
- Pick a story where you made the decision, not one where you watched it.
- State the situation in two sentences and spend the rest on the reasoning.
- Give the blast radius: what could have broken, and what you measured.
- Name the disagreement and how you resolved it with evidence.
Follow-up
- What would you do differently if you ran that again?
- How did you know your change caused the improvement?
Describe a situation where you had to collaborate with a difficult team member.
Describe a situation where you had to collaborate 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 tasks when you have multiple deadlines?
How do you prioritize 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?
Tell me about a time you took the lead on a project. What was the outcome?
Tell me about a time you took the lead on a project. What was the outcome?
Approach
- Pick a story where you made the decision, not one where you watched it.
- State the situation in two sentences and spend the rest on the reasoning.
- Give the blast radius: what could have broken, and what you measured.
- Name the disagreement and how you resolved it with evidence.
Follow-up
- What would you do differently if you ran that again?
- How did you know your change caused the improvement?
How do you handle feedback, both giving and receiving?
How do you handle feedback, both giving and receiving?
Approach
- Pick a story where you made the decision, not one where you watched it.
- State the situation in two sentences and spend the rest on the reasoning.
- Give the blast radius: what could have broken, and what you measured.
- Name the disagreement and how you resolved it with evidence.
Follow-up
- What would you do differently if you ran that again?
- How did you know your change caused the improvement?
What motivates you to excel in your work?
What motivates you to excel in your work?
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?
Explain a time when you had to think outside the box to solve a problem.
Explain a time when you had to think outside the box to solve a problem.
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
What is your experience with version control systems, such as Git?
- 02
Describe a situation where you had to collaborate with a difficult team member.
- 03
How do you prioritize tasks when you have multiple deadlines?
- 04
Tell me about a time you took the lead on a project. What was the outcome?
How difficult is the interview process, and how much preparation time is typical?
The interview process can be moderately challenging, requiring a solid understanding of technical concepts and problem-solving skills. Candidates often recommend at least 2-4 weeks of focused preparation to feel confident.
ESS Software Engineer candidate reports ↗What differentiates successful candidates?
Successful candidates typically demonstrate a strong combination of technical expertise, effective communication skills, and a collaborative mindset. They also align well with the values and culture at ESS.
ESS Software Engineer candidate reports ↗What is the culture and working style at ESS?
ESS fosters a collaborative and innovative culture where teamwork and open communication are highly valued. Employees are encouraged to share ideas and contribute to continuous improvement.
ESS Software Engineer candidate reports ↗What is the typical timeline from the initial screen to an offer?
The timeline can vary but typically ranges from 2-4 weeks, depending on the availability of interviewers and the number of candidates.
ESS Software Engineer candidate reports ↗Are there options for remote or hybrid work?
ESS offers flexible work arrangements, including remote and hybrid options, depending on the position and team requirements.
ESS Software Engineer candidate reports ↗How many interview rounds does ESS have for a Software Engineer, and what are the stages?
For Software Engineer candidates at ESS, the loop starts with a recruiter call for background and role fit. After that, you go through one or more technical interviews that can include coding assessments or system design discussions. The process also includes behavioral questions to understand how you work and communicate.
ESS Software Engineer candidate reports ↗How hard is the ESS Software Engineer interview, based on candidate-reported difficulty?
Candidates who reported on ESS Software Engineer interviews most often described the difficulty as average. Among the reported interviews, there were 9 total observations, and none were categorized as easy or hard in the provided summary.
ESS Software Engineer candidate reports ↗What topics does ESS test for Software Engineers?
ESS interview preparation should cover communication in a technical interview context, reliability engineering, and systems reliability and availability concepts. There is also emphasis on data privacy and confidentiality, including NDA awareness, plus technical fundamentals and electrical engineering fundamentals. The role may include scheduling coordination and broader theoretical understanding.
ESS Software Engineer candidate reports ↗Does ESS Software Engineer testing include coding or system design?
Yes. The technical portion can include coding assessments, and it may also involve system design discussions. You should be ready to explain how you would optimize for performance and resolve a high-stakes technical problem.
ESS Software Engineer candidate reports ↗How many different question types are in the ESS Software Engineer question bank?
The provided question bank size is 24. That suggests you should practice multiple patterns across the technical, system design, and behavioral areas, rather than memorizing a single set of answers.
ESS 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.
- 01ESS 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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