cswork / libraryOpen practice workspace

Interview guides · Greeksoft Technologies

Greeksoft Technologies Software Engineer Interview Guide

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

The 60-second brief

As a Software Engineer at Greeksoft Technologies, you are at the heart of the company’s ability to deliver robust, high-performance solutions. The role is critical to the organization's mission of maintaining technical excellence, often requiring you to navigate both modern development practices and the maintenance of legacy systems. You will contribute to products that demand high reliability and precise engineering, making your ability to write clean, efficient code a primary driver of project success. The work environment at Greeksoft Technologies is characterized by a strong emphasis on core computer science fundamentals. Whether you are working on new feature development or optimizing existing architectures, you will be expected to demonstrate a deep understanding of how your code interacts with system memory and hardware.

This guide is scoped to a Software Engineer candidate at Greeksoft Technologies.

Focus areas

  • C++
  • Object-Oriented Programming (OOP)
  • Data Structures

The Greeksoft Technologies interview process

Greeksoft Technologies candidates report 4 rounds over 3-5 weeks. The stages below are what candidates describe, not a published process.

Initial Screening

Gauge baseline knowledge of candidates to assess their suitability for the role.

What to demonstrate

  • Gauge baseline knowledge of candidates to assess their suitability for the role
  • Depth in C++

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 Assessment Rounds

Multiple rounds focusing on theoretical foundations and practical coding applications.

What to demonstrate

  • Multiple rounds focusing on theoretical foundations and practical coding applications
  • Depth in C++

How to prepare

  • Answer aloud and timed: Can you explain the difference between a constructor and a destructor?
  • Answer aloud and timed: What is memory garbage collection, and how does it impact application performance?

Written Tests

Involve written tests or pen-and-paper coding exercises to evaluate technical skills.

What to demonstrate

  • Involve written tests or pen-and-paper coding exercises to evaluate technical skills
  • Depth in C++

How to prepare

  • Answer aloud and timed: How do you manage pointers and templates effectively in C++?
  • Answer aloud and timed: Can you explain the Standard Template Library (STL) and the use of vectors and queues?

Face-to-Face Discussions

Engage in technical discussions to defend technical decisions and demonstrate knowledge.

What to demonstrate

  • Engage in technical discussions to defend technical decisions and demonstrate knowledge
  • Depth in C++

How to prepare

  • Answer aloud and timed: How would you find the intersection point of two linked lists?
  • Answer aloud and timed: What are the most efficient ways to manipulate arrays and strings to solve a given problem?

Where candidates lose points

Prioritize the Fundamentals

Do not skip the basics. The interviewers will test your knowledge of C/C++ memory management and OOPs principles thoroughly.

Practice Paper Coding

Since some rounds are pen-and-paper based, practice writing code without the help of an IDE’s autocomplete features.

Be Ready to Justify

If you get a question wrong in a test, be prepared to explain your thought process and how you would correct it later.

Stay Calm Under Pressure

The technical rounds can be intensive; if you get stuck, communicate your thought process out loud so the interviewer can guide you.

Questions & practice

What is memory garbage collection, and how does it impact application performance?

Medium · Technical Fundamentals and OOPs

Approach

  1. Say what the runtime actually does before reasoning about the code.
  2. Name what is shared across threads and what owns each piece of state.
  3. Identify the window where an invariant is briefly untrue.
  4. 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?

How do you manage pointers and templates effectively in C++?

Medium · Technical Fundamentals and OOPs

Approach

  1. Say what the runtime actually does before reasoning about the code.
  2. Name what is shared across threads and what owns each piece of state.
  3. Identify the window where an invariant is briefly untrue.
  4. 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?

Can you explain the Standard Template Library (STL) and the use of vectors and queues?

Medium · Data Structures and Algorithms

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?

How would you find the intersection point of two linked lists?

Medium · Data Structures and Algorithms

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 most efficient ways to manipulate arrays and strings to solve a given problem?

Medium · Data Structures and Algorithms

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?

How do you approach designing a circuit based on a provided waveform?

Medium · Data Structures and Algorithms

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?

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?

Write the update path that detects a concurrent edit

Medium · optimistic concurrency · transactional outbox · audit history

resource carries version INT NOT NULL DEFAULT 1. resource_revision holds revision_id, resource_id, version, actor_user_id, change_kind, patch JSONB, request_id, created_at with UNIQUE (resource_id, version). outbox_event holds aggregate_type, aggregate_id, aggregate_version, event_type, payload, status. A PUT carries the version the client read. Write the exact statements for the single transaction that applies the edit, records the revision and enqueues 'resource.updated', and give the handler's branch on zero affected rows. Then say what PostgreSQL 16 does under READ COMMITTED when two of these updates hit one row at once.

Approach

  1. One transaction, three writes, no network call inside it: UPDATE resource SET title = $3, version = version + 1, updated_at = now() WHERE resource_id = $1 AND tenant_id = $4 AND version = $2; then INSERT the resource_revision row at version $2 + 1; then INSERT the outbox_event row at the same aggregate_version. The event goes to a table rather than a broker because no transaction spans both.
  2. Branch on the affected-row count before doing anything else. Zero has three causes — stale version, wrong tenant, row gone — so re-read once and map to 409 carrying the current version, or 404 for an id outside the caller's tenant, which also stops the endpoint confirming that another tenant's id exists.
  3. State the engine behaviour instead of assuming it. Under READ COMMITTED the second UPDATE blocks on the row lock, and when the first commits PostgreSQL re-evaluates the WHERE clause against the newly committed row, so the version predicate now fails and the statement reports zero rows. Under REPEATABLE READ the identical collision raises SQLSTATE 40001 instead, so the handler must fold both shapes into one conflict response.
  4. Keep UNIQUE (resource_id, version) even though the predicate already serialises writers. It is what makes a lost update unwritable if any other path ever reaches the revision table, and it converts a logic bug into 23505 rather than into a silently missing history row.

Follow-up

  • A client sends the version it read ten minutes ago and the resource has moved three versions. What is in your 409 so it can resolve the conflict without a full re-fetch?
  • Two editors, two disjoint fields, no overlap. Does your answer still refuse the second write, and should it?

What are the four pillars of Object-Oriented Programming (Inheritance, Polymorphism, Encapsulation, Abstractio

Medium · Technical Fundamentals and OOPs

What are the four pillars of Object-Oriented Programming (Inheritance, Polymorphism, Encapsulation, Abstraction)?

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 does a VTable work in the context of Run-Time Polymorphism?

Medium · Technical Fundamentals and OOPs

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?

Can you explain the difference between a constructor and a destructor?

Medium · Technical Fundamentals and OOPs

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?

One customer endpoint stalls deliveries to every other destination

Medium · bulkhead · timeouts · saturation

The egress service delivers about 1.5k webhooks/second across 40,000 destinations, with a per-destination concurrency cap of 4 and a 10-second connect-plus-read timeout. Throughput falls to 300/second, queue depth climbs, and p99 delivery latency for unaffected destinations goes from 200 ms to minutes, while the error rate barely moves. One tenant holds 900 destination rows whose URLs share a hostname that now answers in 9.5 seconds. Explain the mechanism with the arithmetic, then give the containment in the order you would apply it.

Approach

  1. Look at saturation before errors. A flat error rate with collapsing throughput says nothing is failing, things are waiting, so the first signal to pull is in-flight request count or pool wait time rather than the error counter. This is the distinction that decides the whole investigation.
  2. Group in-flight work by resolved host, not by destination id. The cap is keyed per destination row, so 900 rows sharing one hostname buy 3,600 concurrent slots against a single host, each held for 9.5 seconds. The bulkhead was never a bulkhead for that host, and grouping by the wrong dimension is why the dashboard looked healthy.
  3. Do the arithmetic in both directions. Required concurrency is arrival rate times latency, so 1.5k/second at 200 ms needs about 300 in flight, which is entirely consumed by 3,600 slow slots; conversely whatever concurrency is left sustains rate equals concurrency divided by 9.5 seconds, which is the 300/second you are seeing. Matching both numbers is what promotes this from a plausible story to the mechanism.
  4. Explain why the circuit breaker never helped. It opens on consecutive failures, and a 9.5-second response inside a 10-second timeout is a success. Slow is not failing, so an error-rate breaker cannot see this; you need a slow-call ratio, a deadline propagated from the caller's remaining budget, or a concurrency limiter.

Follow-up

  • The host recovers to 80 ms. How long does the queue take to drain, and what does the drain do to the recovered host?
  • Where should the 10-second timeout number actually come from?

Suggested practice checklist

Built from the rounds and topics Greeksoft Technologies candidates report.

Day 1 — Map the Greeksoft Technologies loop

  • Write out the reported sequence: Initial Screening, Technical Assessment Rounds, Written Tests, Face-to-Face Discussions.
  • 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.

Day 2 — Work C++

  • Spend the session on C++, which Greeksoft Technologies candidates report being tested on.
  • Write one worked example in C++ and time yourself on it.

Deliverable: One timed worked example in C++.

Day 3 — Work Object-Oriented Programming (OOP)

  • Spend the session on Object-Oriented Programming (OOP), which Greeksoft Technologies candidates report being tested on.
  • Write one worked example in Object-Oriented Programming (OOP) and time yourself on it.

Deliverable: One timed worked example in Object-Oriented Programming (OOP).

Day 4 — Work Data Structures

  • Spend the session on Data Structures, which Greeksoft Technologies candidates report being tested on.
  • Write one worked example in Data Structures and time yourself on it.

Deliverable: One timed worked example in Data Structures.

Day 5 — Answer out loud: Technical Fundamentals and OOPs

  • Answer aloud, timed: What are the four pillars of Object-Oriented Programming (Inheritance, Polymorphism, Encapsulation, Abstraction)?
  • Answer aloud, timed: How does a VTable work in the context of Run-Time Polymorphism?

Deliverable: Spoken answers to 2 reported Technical Fundamentals and OOPs question(s), under time.

Day 6 — Answer out loud: Data Structures and Algorithms

  • Answer aloud, timed: Can you explain the Standard Template Library (STL) and the use of vectors and queues?
  • Answer aloud, timed: How would you find the intersection point of two linked lists?

Deliverable: Spoken answers to 2 reported Data Structures and Algorithms question(s), under time.

Day 7 — Answer out loud: Behavioral and Process-Oriented

  • Answer aloud, timed: Can you justify the logic you used to solve the problems in the written test?
  • Answer aloud, timed: How do you handle your responsibilities when faced with technical ambiguity?

Deliverable: Spoken answers to 2 reported Behavioral and Process-Oriented question(s), under time.

Behavioural preparation

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

Can you justify the logic you used to solve the problems in the written test?

Medium · Behavioral and Process-Oriented

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 your responsibilities when faced with technical ambiguity?

Medium · Behavioral and Process-Oriented

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 revisited a problem after an interview to ensure you understood the solution.

Medium · Behavioral and Process-Oriented

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?