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Depcom Power Software Engineer Interview Guide

Depcom Power Software Engineer interview guide: reported rounds, questions and how candidates describe the process.

The 60-second brief

At Depcom Power, a Software Engineer plays a crucial role in building and maintaining the digital infrastructure that powers utility-scale solar energy projects. Unlike typical tech companies where software is the end product, software engineering at Depcom Power directly enables the engineering, procurement, construction (EPC), and operations and maintenance (O&M) of massive clean energy installations. The tools and platforms you build and optimize will directly impact how solar plants are designed, how supply chains are managed, and how real-time performance data is analyzed. You will work on a variety of internal systems, ranging from proprietary solar estimation and engineering design tools to data pipelines that monitor solar asset performance.

This guide is scoped to a Software Engineer candidate at Depcom Power.

Focus areas

  • Software Engineering (General)
  • Resume-Based Technical Evaluation
  • Behavioral Interviewing / Background Questions

The Depcom Power interview process

Depcom Power candidates report 3 rounds over 3-5 weeks. The stages below are what candidates describe, not a published process.

Initial Screening Call

A call with a recruiter to discuss your background and assess fit for the team.

What to demonstrate

  • A call with a recruiter to discuss your background and assess fit for the team
  • Depth in Software Engineering (General)

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 Panel Interview

A panel interview conducted via Microsoft Teams with multiple team members reviewing your resume.

What to demonstrate

  • A panel interview conducted via Microsoft Teams with multiple team members reviewing your resume
  • Depth in Software Engineering (General)

How to prepare

  • Answer aloud and timed: What technologies are you most comfortable with, and how did you choose them for your recent projects?
  • Answer aloud and timed: Tell me about a time you had to work with a legacy codebase. How did you navigate it and implement new features?

In-Person Interview

Possible invitation for an in-person interview at one of the main offices, depending on location and team.

What to demonstrate

  • Possible invitation for an in-person interview at one of the main offices, depending on location and team
  • Depth in Software Engineering (General)

How to prepare

  • Answer aloud and timed: How do you ensure code quality and maintainability when working in a fast-paced environment with shifting priorities?
  • Answer aloud and timed: How would you design a simple database schema to track inventory and shipping logistics for a large-scale construction project?

Where candidates lose points

Master your resume narrative

Be ready to explain the "why" behind every technical decision on your resume. The interviewers will use your past experiences as the primary way to gauge your technical depth.

Understand the business context

Take some time to learn about utility-scale solar projects and the EPC (Engineering, Procurement, and Construction) model. Showing that you understand how Depcom Power operates will set you apart from other candidates.

Communication styles can sometimes be highly informal

Be proactive about scheduling and confirming your interview times, and do not hesitate to reach out to your recruiter if there is a delay in feedback after a major interview round.

Questions & practice

Explain the difference between a relational database and a non-relational database. When would you choose one

Medium · Practical Technical & Problem Solving

Explain the difference between a relational database and a non-relational database. When would you choose one over the other?

Approach

  1. Restate the input: its shape, its size, and what is guaranteed about it.
  2. Name the brute-force solution and its complexity before improving on it.
  3. Choose the data structure from the access pattern, not from familiarity.
  4. 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?

Describe how you would write a script to automate a repetitive data entry task that our engineering team curre

Medium · Practical Technical & Problem Solving

Describe how you would write a script to automate a repetitive data entry task that our engineering team currently does manually.

Approach

  1. Restate the input: its shape, its size, and what is guaranteed about it.
  2. Name the brute-force solution and its complexity before improving on it.
  3. Choose the data structure from the access pattern, not from familiarity.
  4. 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?

What are the key security considerations you keep in mind when building internal web applications?

Medium · Practical Technical & Problem Solving

Approach

  1. Restate the input: its shape, its size, and what is guaranteed about it.
  2. Name the brute-force solution and its complexity before improving on it.
  3. Choose the data structure from the access pattern, not from familiarity.
  4. 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 why the owner filter ignores the listing index

Medium · composite index · query plans · sort elimination

The only index on resource is (tenant_id, status, updated_at DESC, resource_id DESC). A new endpoint returns one user's resources across all statuses, newest created first: WHERE tenant_id = $1 AND owner_user_id = $2 ORDER BY created_at DESC LIMIT 20. On a tenant with 2M rows it takes 900 ms and EXPLAIN shows a sort above a large scan. Explain precisely why the existing index cannot serve it, give the index that can, and state which of these the new index still will not help: owner_user_id alone across tenants; the same query ordered by updated_at. PostgreSQL 16.

Approach

  1. Separate the two jobs an index does. For filtering, a composite btree is seekable only on a left prefix, so with no predicate on status the scan can at best range over tenant_id and test owner_user_id per row; PostgreSQL 16 has no btree skip scan to jump the unconstrained column.
  2. For ordering, the index is sorted by (status, updated_at) within a tenant and not by created_at, so the LIMIT cannot stop early: every matching row is read and then sorted. That is the 'Sort Method: top-N heapsort' line, and it is why the plan reads 2M rows to answer with 20.
  3. Derive the replacement from the access path — equality, equality, then the ordering column: CREATE INDEX CONCURRENTLY ON resource (tenant_id, owner_user_id, created_at DESC). The scan seeks to the (tenant, owner) range and walks 20 entries in order, so the Sort node disappears along with the row-read.
  4. Treat INCLUDE (title, status) as conditional, not free. An index-only scan still visits the heap for any row whose page is not marked all-visible, so on a table taking 1.2k writes/second the win depends on autovacuum keeping the visibility map current, and the wider index costs more on every insert.

Follow-up

  • 90% of rows are status='active'. Would a partial index WHERE status = 'active' change your answer, and for which of the three queries?
  • A dashboard runs this for 40 owners in one page load. What changes about the design?

Stop tag and share joins from fanning out a page

Medium · join fan-out · semi-joins · many-to-many

resource_tag is (resource_id, tag_id) with PK (resource_id, tag_id); resource_share is (resource_id, shared_with_user_id, permission). The tagged-and-shared listing inner-joins resource to both, filters tenant_id, tag_id = ANY($2) and shared_with_user_id = $3, orders by updated_at DESC and takes 50. Pages come back with fewer than 50 distinct resources and the total in the header is far too high. Explain the row multiplication, rewrite both the page query and the count query so each is correct, and name the index each one needs. PostgreSQL 16.

Approach

  1. Do the arithmetic against the predicates that are actually there. An inner join emits one row per matching child row, and both joins are filtered: tag_id = ANY($2) admits only the requested tags, shared_with_user_id = $3 admits one user's share rows. So a resource holding three of the requested tags and shared with $3 once yields three rows, not one — the multiplier is its count of matching tags times its share rows for that single user, and that second factor is 1 unless the table admits duplicate (resource_id, shared_with_user_id) pairs. LIMIT 50 then limits rows rather than resources, and COUNT(*) counts pairs — the header is the product, not the population.
  2. Reject DISTINCT as the fix. It deduplicates after the product has been built, so the planner must materialise and sort the fanned-out set before the LIMIT can apply, and it leaves any SUM or AVG in the same select list wrong.
  3. Rewrite both filters as semi-joins, keeping resource as the only row source: AND EXISTS (SELECT 1 FROM resource_tag rt WHERE rt.resource_id = r.resource_id AND rt.tag_id = ANY($2)) and the same shape against resource_share. A semi-join stops at the first match per resource and preserves the driving index order, so ORDER BY updated_at DESC, resource_id DESC LIMIT 50 still stops after 50 rows.
  4. Count with the same predicates and no join at all: SELECT count(*) FROM resource r WHERE r.tenant_id = $1 AND r.status = 'active' AND EXISTS (...) AND EXISTS (...). Nothing multiplies a resource, so the number is the population.

Follow-up

  • The filter changes from 'any of these tags' to 'all of these tags'. Rewrite it and state what it costs relative to the ANY form.
  • A resource can be shared with the same user twice under different permissions. Does your count change, and should it?

Walk me through your resume and highlight a project where you had to make a critical technical trade-off.

Medium · Resume & Professional Experience

Approach

  1. Clarify what is being asked and what a complete answer contains.
  2. State your assumptions explicitly before working the problem.
  3. Say what you would check first and why it is the highest-information step.
  4. 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 software bug you encountered in a past role and how you went about diagnosing and resol

Medium · Resume & Professional Experience

Describe a challenging software bug you encountered in a past role and how you went about diagnosing and resolving it.

Approach

  1. Clarify what is being asked and what a complete answer contains.
  2. State your assumptions explicitly before working the problem.
  3. Say what you would check first and why it is the highest-information step.
  4. 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 technologies are you most comfortable with, and how did you choose them for your recent projects?

Medium · Resume & Professional Experience

Approach

  1. Clarify what is being asked and what a complete answer contains.
  2. State your assumptions explicitly before working the problem.
  3. Say what you would check first and why it is the highest-information step.
  4. Work from the requirement backwards to the design.

Follow-up

  • What assumption would you test first?
  • How would you know your answer was wrong?

How do you ensure code quality and maintainability when working in a fast-paced environment with shifting prio

Medium · Resume & Professional Experience

How do you ensure code quality and maintainability when working in a fast-paced environment with shifting priorities?

Approach

  1. Clarify what is being asked and what a complete answer contains.
  2. State your assumptions explicitly before working the problem.
  3. Say what you would check first and why it is the highest-information step.
  4. 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 simple database schema to track inventory and shipping logistics for a large-scale cons

Medium · Practical Technical & Problem Solving

How would you design a simple database schema to track inventory and shipping logistics for a large-scale construction project?

Approach

  1. Fix the scope first: who calls this, how often, and what they do when it fails.
  2. Name the read and write paths separately; they rarely have the same bottleneck.
  3. Choose a partition key and say what query it makes expensive.
  4. 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 approach API design when you need to integrate multiple third-party services?

Medium · Practical Technical & Problem Solving

Approach

  1. Say who the caller is and what they do when the call fails halfway.
  2. Define the identity of a request so a retry cannot double-apply it.
  3. Separate accepted, pending, failed and confirmed; they are different facts.
  4. 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?

Listing latency scales with page size, not with filters

Easy · n+1 · latency · query batching

The tenant listing endpoint reads resource filtered by tenant_id and status, ordered by updated_at DESC, and returns each row plus the owner's display name from app_user and the actor of that resource's latest resource_revision. p99 is 55 ms at 10 rows per page and 1.4 s at 200. Database telemetry shows 401 statements per request, each under 1 ms, and nothing in the slow-query log. Diagnose the cause and give the fix, stating the statement count per request and the p99 you expect afterwards.

Approach

  1. Read the counters before forming a theory. 401 statements for 200 rows is one driver query plus two per row, and sub-millisecond execution with an empty slow-query log rules out a bad plan. The time is round trips, which is why it is invisible in every per-query metric and scales with rows returned rather than with filter selectivity.
  2. Name the two per-row statements from their normalised text: a single-row app_user lookup by user_id, and a resource_revision lookup by resource_id ordered by version DESC LIMIT 1. Confirm by dropping those two response fields and watching the statement count fall to one. That locates the calls in the serialisation layer, not the repository.
  3. Check that the arithmetic accounts for the whole gap. Measure one round trip to the replica in isolation; 400 trips at roughly 3 ms of network plus 0.2 ms of execution is about 1.3 s on top of a 55 ms baseline, which matches. If the multiplication had fallen short, the N+1 would only be part of the story and you would keep looking.
  4. Batch both lookups. Collect owner_user_ids and resource_ids from the driver query, then issue WHERE tenant_id = $1 AND user_id = ANY($2) for the users, and PostgreSQL's SELECT DISTINCT ON (resource_id) ... WHERE resource_id = ANY($2) ORDER BY resource_id, version DESC for the latest revision, which the UNIQUE (resource_id, version) index serves directly. On an engine without DISTINCT ON, use a lateral join or a row_number window. Three statements per request at any page size.

Follow-up

  • The page size is capped at 200 today. What breaks first if it is raised to 2,000, and is it still this bug?
  • How do you stop the next N+1 from reaching production, given that no individual query is slow and the endpoint's tests pass?

Suggested practice checklist

Built from the rounds and topics Depcom Power candidates report.

Day 1 — Map the Depcom Power loop

  • Write out the reported sequence: Initial Screening Call, Technical Panel Interview, In-Person 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 3 reported rounds, with the weakest marked.

Day 2 — Work Software Engineering (General)

  • Spend the session on Software Engineering (General), which Depcom Power candidates report being tested on.
  • Write one worked example in Software Engineering (General) and time yourself on it.

Deliverable: One timed worked example in Software Engineering (General).

Day 3 — Work Resume-Based Technical Evaluation

  • Spend the session on Resume-Based Technical Evaluation, which Depcom Power candidates report being tested on.
  • Write one worked example in Resume-Based Technical Evaluation and time yourself on it.

Deliverable: One timed worked example in Resume-Based Technical Evaluation.

Day 4 — Work Behavioral Interviewing / Background Questions

  • Spend the session on Behavioral Interviewing / Background Questions, which Depcom Power candidates report being tested on.
  • Write one worked example in Behavioral Interviewing / Background Questions and time yourself on it.

Deliverable: One timed worked example in Behavioral Interviewing / Background Questions.

Day 5 — Answer out loud: Resume & Professional Experience

  • Answer aloud, timed: Walk me through your resume and highlight a project where you had to make a critical technical trade-off.
  • Answer aloud, timed: Describe a challenging software bug you encountered in a past role and how you went about diagnosing and resolving it.

Deliverable: Spoken answers to 2 reported Resume & Professional Experience question(s), under time.

Day 6 — Answer out loud: Practical Technical & Problem Solving

  • Answer aloud, timed: How would you design a simple database schema to track inventory and shipping logistics for a large-scale construction project?
  • Answer aloud, timed: Explain the difference between a relational database and a non-relational database. When would you choose one over the other?

Deliverable: Spoken answers to 2 reported Practical Technical & Problem Solving question(s), under time.

Day 7 — Answer out loud: Behavioral & Cultural Fit

  • Answer aloud, timed: Tell me about a time you had to collaborate with non-technical stakeholders to gather requirements for a software tool.
  • Answer aloud, timed: How do you handle a situation where a team member disagrees with your technical approach or design decision?

Deliverable: Spoken answers to 2 reported Behavioral & Cultural Fit question(s), under time.

Behavioural preparation

Behavioural rounds judge the decision you made and what it cost.

Tell me about a time you had to work with a legacy codebase. How did you navigate it and implement new feature

Medium · Resume & Professional Experience

Tell me about a time you had to work with a legacy codebase. How did you navigate it and implement new features?

Approach

  1. Pick a story where you made the decision, not one where you watched it.
  2. State the situation in two sentences and spend the rest on the reasoning.
  3. Give the blast radius: what could have broken, and what you measured.
  4. Name the disagreement and how you resolved it with evidence.

Follow-up

  • What would you do differently if you ran that again?
  • How did you know your change caused the improvement?

Tell me about a time you had to collaborate with non-technical stakeholders to gather requirements for a softw

Medium · Behavioral & Cultural Fit

Tell me about a time you had to collaborate with non-technical stakeholders to gather requirements for a software tool.

Approach

  1. Pick a story where you made the decision, not one where you watched it.
  2. State the situation in two sentences and spend the rest on the reasoning.
  3. Give the blast radius: what could have broken, and what you measured.
  4. 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 a situation where a team member disagrees with your technical approach or design decision?

Medium · Behavioral & Cultural Fit

Approach

  1. Pick a story where you made the decision, not one where you watched it.
  2. State the situation in two sentences and spend the rest on the reasoning.
  3. Give the blast radius: what could have broken, and what you measured.
  4. 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 time when a project requirement changed mid-way through development. How did you adapt?

Medium · Behavioral & Cultural Fit

Approach

  1. Pick a story where you made the decision, not one where you watched it.
  2. State the situation in two sentences and spend the rest on the reasoning.
  3. Give the blast radius: what could have broken, and what you measured.
  4. Name the disagreement and how you resolved it with evidence.

Follow-up

  • What would you do differently if you ran that again?
  • How did you know your change caused the improvement?

Why are you interested in working in the renewable energy sector, specifically with Depcom Power?

Medium · Behavioral & Cultural Fit

Approach

  1. Pick a story where you made the decision, not one where you watched it.
  2. State the situation in two sentences and spend the rest on the reasoning.
  3. Give the blast radius: what could have broken, and what you measured.
  4. 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 manage your time and prioritize tasks when working on multiple projects simultaneously?

Medium · Behavioral & Cultural Fit

Approach

  1. Pick a story where you made the decision, not one where you watched it.
  2. State the situation in two sentences and spend the rest on the reasoning.
  3. Give the blast radius: what could have broken, and what you measured.
  4. 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?