As a Software Engineer at Sunrun, you play a crucial role in developing and enhancing the software systems that support our mission of making solar energy accessible to everyone. This position is integral to ensuring that our products are not only efficient but also user-friendly, thus directly impacting customer satisfaction and business growth. You will be working on a range of innovative software solutions that facilitate solar energy management, customer engagement, and operational efficiency. The complexity and scale of the projects you will be involved in require an agile mindset and a passion for technology. You will collaborate with cross-functional teams, including product managers, data scientists, and other engineers, to design, develop, and implement software that meets the dynamic needs of the solar industry. This role is not just about writing code; it’s about contributing to a sustainable future and making a tangible difference in the lives of our customers.
Initial Screening
reportedScreening conducted by HR to assess candidate suitability for the role.
What to demonstrate
- Screening conducted by HR to assess candidate suitability for the role
- Depth in System Design
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
reportedMultiple rounds of technical interviews including coding challenges and system design discussions.
What to demonstrate
- Multiple rounds of technical interviews including coding challenges and system design discussions
- Depth in System Design
How to prepare
- Answer aloud and timed: How does dependency injection work, and why is it beneficial?
- Answer aloud and timed: Describe the use of Hibernate in Java applications.
Behavioral Assessments
reportedEvaluation of cultural fit and behavioral responses during the interview process.
What to demonstrate
- Evaluation of cultural fit and behavioral responses during the interview process
- Depth in System Design
How to prepare
- Prepare three examples from your own work, each with a decision you made and an outcome you can quantify.
- Re-read the description of the behavioral assessments above and write down what you would ask to confirm before it.
PracHub editorial advice for the preparation topics above.
Research the Company
Familiarize yourself with Sunrun's mission, values, and recent initiatives in solar technology. This knowledge can help you align your responses with the company's goals.
Practice Coding
Use platforms like LeetCode or HackerRank to practice coding problems. Focus on algorithms and data structures to prepare for technical assessments.
Prepare Questions
Have insightful questions ready to ask your interviewers about the team dynamics, project goals, and company culture.
Show Enthusiasm
Express your passion for technology and renewable energy solutions during the interview. This can resonate well with the interviewers at Sunrun.
Choose a category, try a prompt, then open its approach, worked solution or follow-up when you need it.
What is an associative array, and how does it differ from other data structures?
What is an associative array, and how does it differ from other data structures?
Approach
- Restate the input: its shape, its size, and what is guaranteed about it.
- Name the brute-force solution and its complexity before improving on it.
- Choose the data structure from the access pattern, not from familiarity.
- State the target complexity and say which constraint rules the naive version out.
Follow-up
- How does this change if the input no longer fits in memory?
- What is the worst case, and how likely is it on real data?
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?
Given an array of integers, find two numbers that sum to a specific target.
Given an array of integers, find two numbers that sum to a specific target.
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?
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?
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?
Can you explain the differences between `final`, `finally`, and `finalize` in Java?
Can you explain the differences between final, finally, and finalize in Java?
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 does dependency injection work, and why is it beneficial?
How does dependency injection work, and why is it beneficial?
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 the use of Hibernate in Java applications.
Describe the use of Hibernate in Java applications.
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 differences between checked and unchecked exceptions?
What are the differences between checked and unchecked exceptions?
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 for managing solar energy data?
How would you design a system for managing solar energy data?
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 when designing a cloud-based application?
What considerations would you take into account when designing a cloud-based application?
Approach
- Fix the scope first: who calls this, how often, and what they do when it fails.
- Name the read and write paths separately; they rarely have the same bottleneck.
- Choose a partition key and say what query it makes expensive.
- State the consistency you need, and where you are willing to be stale.
Follow-up
- What breaks first when traffic grows ten times?
- How does this behave when that dependency is down for an hour?
Given a set of requirements, how would you determine the best technology stack to use?
Given a set of requirements, how would you determine the best technology stack to use?
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 performance issue in a web application?
How would you approach debugging a performance issue in a web application?
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 Sunrun candidates report.
Prepare, practise & reflect
One practical outcome each day. Spend longer where you need it.
0 / 7 done01Map the Sunrun loop
- Write out the reported sequence: Initial Screening, Technical Interviews, Behavioral Assessments.
- 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 System Design
- Spend the session on System Design, which Sunrun candidates report being tested on.
- Write one worked example in System Design and time yourself on it.
Deliverable: One timed worked example in System Design.
03Work JavaScript
- Spend the session on JavaScript, which Sunrun candidates report being tested on.
- Write one worked example in JavaScript and time yourself on it.
Deliverable: One timed worked example in JavaScript.
04Work React
- Spend the session on React, which Sunrun candidates report being tested on.
- Write one worked example in React and time yourself on it.
Deliverable: One timed worked example in React.
05Answer out loud: Technical / Domain Questions
- Answer aloud, timed: What is an associative array, and how does it differ from other data structures?
- Answer aloud, timed: Can you explain the differences between `final`, `finally`, and `finalize` in Java?
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 for managing solar energy data?
- Answer aloud, timed: What considerations would you take into account when designing a cloud-based application?
Deliverable: Spoken answers to 2 reported System Design / Architecture question(s), under time.
07Answer out loud: Behavioral / Leadership
- Answer aloud, timed: Describe a challenging project you worked on. How did you handle the challenges?
- Answer aloud, timed: How do you prioritize tasks when working on multiple projects simultaneously?
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.
Describe a time when you had to refactor a piece of software. What was the outcome?
Describe a time when you had to refactor a piece of software. 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?
Describe a challenging project you worked on. How did you handle the challenges?
Describe a challenging project you worked on. How did you handle the challenges?
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 working on multiple projects simultaneously?
How do you prioritize tasks when working on multiple projects simultaneously?
Approach
- Pick a story where you made the decision, not one where you watched it.
- State the situation in two sentences and spend the rest on the reasoning.
- Give the blast radius: what could have broken, and what you measured.
- Name the disagreement and how you resolved it with evidence.
Follow-up
- What would you do differently if you ran that again?
- How did you know your change caused the improvement?
Can you give an example of how you handled a conflict in a team setting?
Can you give an example of how you handled a conflict in a team setting?
Approach
- Pick a story where you made the decision, not one where you watched it.
- State the situation in two sentences and spend the rest on the reasoning.
- Give the blast radius: what could have broken, and what you measured.
- Name the disagreement and how you resolved it with evidence.
Follow-up
- What would you do differently if you ran that again?
- How did you know your change caused the improvement?
- 01
Describe a time when you had to refactor a piece of software. What was the outcome?
- 02
Describe a challenging project you worked on. How did you handle the challenges?
- 03
How do you prioritize tasks when working on multiple projects simultaneously?
- 04
Can you give an example of how you handled a conflict in a team setting?
How difficult are the interviews at Sunrun?
The difficulty can vary depending on the role and the specific interviewers, but candidates often report an average level of challenge with a mix of technical and behavioral questions.
Sunrun Software Engineer candidate reports ↗What differentiates successful candidates?
Candidates who demonstrate strong technical skills, clear problem-solving abilities, and a good cultural fit with Sunrun tend to stand out.
Sunrun Software Engineer candidate reports ↗How long does the interview process typically take?
The timeline from initial screening to offer can vary, but candidates should expect a few weeks of interviews, including follow-ups.
Sunrun Software Engineer candidate reports ↗What is the company culture like at Sunrun?
Sunrun fosters a collaborative and innovative culture, emphasizing sustainability and a commitment to providing excellent customer service.
Sunrun Software Engineer candidate reports ↗What topics does Sunrun test in interviews?
Sunrun interviews most often cover Stakeholder Communication, JavaScript, Stakeholder Management, Java, and Logging. The exact emphasis depends on the specific role you apply for.
Sunrun 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.
- 01Sunrun 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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