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DONE by NONE Software Engineer Interview Guide

DONE by NONE Software Engineer interview guide: reported rounds, questions and how candidates describe the process.

The 60-second brief

As a Software Engineer at DONE by NONE, you will play a central role in designing, building, and maintaining scalable systems that power core digital experiences. You will operate across the software development lifecycle, translating business requirements into clean, performant, and reliable code. Engineers here work on high-impact projects ranging from core platform services and backend data pipelines to modern web interfaces, ensuring high system availability and seamless operational efficiency. The role demands a balance of solid computer science fundamentals, practical programming proficiency, and structured problem-solving. At DONE by NONE, software engineering is not merely about writing code; it is about building robust architecture, optimizing algorithms, and collaborating across engineering and product teams to solve complex technical challenges.

This guide is scoped to a Software Engineer candidate at DONE by NONE.

Focus areas

  • Linked List
  • Data Structures (General)
  • Object-Oriented Programming (OOP)

The DONE by NONE interview process

DONE by NONE candidates report 5 rounds over 4-6 weeks. The stages below are what candidates describe, not a published process.

Initial Screening

The journey begins with an initial screening round based on the application method.

What to demonstrate

  • The journey begins with an initial screening round based on the application method
  • Depth in Linked List

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.

Online/Written Test

A timed assessment covering quantitative aptitude, logical reasoning, and core computer science concepts.

What to demonstrate

  • A timed assessment covering quantitative aptitude, logical reasoning, and core computer science concepts
  • Depth in Linked List

How to prepare

  • Answer aloud and timed: Explain the logic and implementation for checking whether a given string or number is a palindrome.
  • Answer aloud and timed: Compare dynamic array implementations with linked lists in terms of memory overhead and time complexity for insertion and deletion operations.

Technical Interview Rounds

One or two rounds focusing on live coding, data structures, OOP concepts, networking, and software design principles.

What to demonstrate

  • One or two rounds focusing on live coding, data structures, OOP concepts, networking, and software design principles
  • Depth in Linked List

How to prepare

  • Answer aloud and timed: How do local and global variables differ regarding memory scope, stack allocation, and lifecycle within a program?
  • Answer aloud and timed: Define encapsulation and polymorphism, providing real-world code examples demonstrating their implementation.

Managerial Review

Final stages include managerial and behavioral evaluations.

What to demonstrate

  • Final stages include managerial and behavioral evaluations
  • Depth in Linked List

How to prepare

  • Answer aloud and timed: How does inheritance differ from composition, and when would you choose one over the other in software architecture?
  • Answer aloud and timed: Explain fundamental JavaScript concepts such as execution context, closure, and event loop mechanics.

HR Discussion

Concludes the interview process with a comprehensive discussion with HR.

What to demonstrate

  • Concludes the interview process with a comprehensive discussion with HR
  • Depth in Linked List

How to prepare

  • Answer aloud and timed: What are the core differences between functional components and class components in React?
  • Answer aloud and timed: Discuss the key principles of modern Java development, including memory management and garbage collection basics.

Where candidates lose points

Review CS Core Subjects Rigorously

Re-acquaint yourself with standard textbook topics in OS, Computer Networks (OSI layers, routing), DBMS, and OOP concepts like encapsulation and polymorphism.

Practice In-Place Data Manipulation

Work through basic algorithmic challenges—such as finding maximum numbers, reversing strings, or checking palindromes—without relying on automated built-in sort functions.

Structure Your Behavioral Responses

Use the STAR method (Situation, Task, Action, Result) to concisely communicate your past project accomplishments, team interactions, and technical contributions.

Questions & practice

Explain how a linked list manages dynamic data elements and describe the structure of a node containing data a

Medium · Computer Science Fundamentals & Data Str

Explain how a linked list manages dynamic data elements and describe the structure of a node containing data and memory pointers.

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?

Write a program to find the maximum and second maximum numbers in an unsorted array without using built-in sor

Medium · Computer Science Fundamentals & Data Str

Write a program to find the maximum and second maximum numbers in an unsorted array without using built-in sorting 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?

Explain the logic and implementation for checking whether a given string or number is a palindrome.

Medium · Computer Science Fundamentals & Data Str

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?

Compare dynamic array implementations with linked lists in terms of memory overhead and time complexity for in

Medium · Computer Science Fundamentals & Data Str

Compare dynamic array implementations with linked lists in terms of memory overhead and time complexity for insertion and deletion operations.

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 local and global variables differ regarding memory scope, stack allocation, and lifecycle within a prog

Medium · Computer Science Fundamentals & Data Str

How do local and global variables differ regarding memory scope, stack allocation, and lifecycle within a program?

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?

Define encapsulation and polymorphism, providing real-world code examples demonstrating their implementation.

Medium · Object-Oriented Programming & Language P

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?

Explain fundamental JavaScript concepts such as execution context, closure, and event loop mechanics.

Medium · Object-Oriented Programming & Language P

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?

What are the core differences between functional components and class components in React?

Medium · Object-Oriented Programming & Language P

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?

Discuss the key principles of modern Java development, including memory management and garbage collection basi

Medium · Object-Oriented Programming & Language P

Discuss the key principles of modern Java development, including memory management and garbage collection basics.

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?

Explain the key differences between process management and threading within modern operating systems.

Medium · Computer Networks, Operating Systems & D

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?

Describe the principles of DBMS normalization and explain how indexing improves query performance.

Medium · Computer Networks, Operating Systems & D

Approach

  1. Name the grain you start from and join outward from it.
  2. Check whether any join is one-to-many before aggregating, or the sums inflate.
  3. Say which index the query would use, and what makes it unusable.
  4. Handle the rows that do not match: that is usually the actual question.

Follow-up

  • How does the query change if that join becomes one-to-many?
  • What happens to this when the table is ten times larger?

Keep soft-deleted accounts from blocking re-registration

Easy · soft delete · unique constraints · engine differences

app_user holds user_id, tenant_id, email CITEXT, password_hash (NULL for SSO principals), email_verified_at, auth_version, status ('invited','active','suspended','deactivated'), created_at, updated_at, deleted_at. Two live accounts for one address inside a tenant must be impossible, but an address freed by a soft delete must be reusable, and the same tenant may delete and re-register it repeatedly. Write the uniqueness DDL for PostgreSQL 16, then the equivalent for MySQL 8 where partial indexes do not exist, and say what each permits once three deleted rows already hold that address.

Approach

  1. Start from what is actually unique: not (tenant_id, email), but (tenant_id, email) among live rows. PostgreSQL says that directly — CREATE UNIQUE INDEX app_user_live_email ON app_user (tenant_id, email) WHERE deleted_at IS NULL. A full constraint over the same two columns burns the address permanently the first time someone deletes an account.
  2. Keep case-insensitivity in the type or the index, never in the application: CITEXT as given, or UNIQUE (tenant_id, lower(email)) as an expression index where the extension is unavailable. A case-sensitive unique column is exactly how two accounts for one human appear.
  3. For MySQL 8 the predicate has to move inside the key: add a discriminator column that is a constant 0 while the row is live and is set to user_id on delete, with UNIQUE (tenant_id, email, deleted_marker). Live rows share the constant and still collide; deleted rows differ from each other and stop colliding.
  4. State the NULL variant and its dependency: leaving the marker NULL for deleted rows also works, because a unique index treats NULLs as distinct — true in MySQL, and true in PostgreSQL only under the default NULLS DISTINCT, which PostgreSQL 15 lets you reverse. Check the polarity against the three existing deleted rows: constant-on-live is what preserves the collision you want, and reversing it silently admits duplicate live accounts.

Follow-up

  • A deleted account re-registers with the same address the next day. Do the old resource rows follow the new user_id, and how does the API keep the two principals apart?
  • How do you honour an erasure request while resource_revision.actor_user_id still references this table?

How does inheritance differ from composition, and when would you choose one over the other in software archite

Medium · Object-Oriented Programming & Language P

How does inheritance differ from composition, and when would you choose one over the other in software architecture?

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?

Walk through the seven layers of the OSI model and explain the function of routing and switching at the networ

Medium · Computer Networks, Operating Systems & D

Walk through the seven layers of the OSI model and explain the function of routing and switching at the network layer.

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 are microservices, and how do they differ from monolithic system architecture?

Medium · Computer Networks, Operating Systems & D

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 non-functional requirements like system security, network latency, and availability influence software

Medium · Computer Networks, Operating Systems & D

How do non-functional requirements like system security, network latency, and availability influence software design?

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?

Explain the difference between functional and non-functional software testing.

Medium · Software Testing & Quality Assurance Pri

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?

Compare alpha testing and beta testing in terms of environment, user groups, and product release stages.

Medium · Software Testing & Quality Assurance Pri

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?

Explain the fundamental difference between load testing and stress testing when evaluating application resilie

Medium · Software Testing & Quality Assurance Pri

Explain the fundamental difference between load testing and stress testing when evaluating application resilience.

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 are the core software testing principles every engineer should follow during development?

Medium · Software Testing & Quality Assurance Pri

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 the key differences between unit, integration, and system test levels.

Medium · Software Testing & Quality Assurance Pri

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?

How do you approach debugging complex technical issues under tight project deadlines?

Medium · Behavioral, Project Leadership & Domain

Approach

  1. Establish what changed and when, before forming any theory.
  2. Pick a bisection that eliminates candidates whichever way it turns out.
  3. Check the instrumentation before believing the symptom.
  4. 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?

Suggested practice checklist

Built from the rounds and topics DONE by NONE candidates report.

Day 1 — Map the DONE by NONE loop

  • Write out the reported sequence: Initial Screening, Online/Written Test, Technical Interview Rounds, Managerial Review, HR Discussion.
  • 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 5 reported rounds, with the weakest marked.

Day 2 — Work Linked List

  • Spend the session on Linked List, which DONE by NONE candidates report being tested on.
  • Write one worked example in Linked List and time yourself on it.

Deliverable: One timed worked example in Linked List.

Day 3 — Work Data Structures (General)

  • Spend the session on Data Structures (General), which DONE by NONE candidates report being tested on.
  • Write one worked example in Data Structures (General) and time yourself on it.

Deliverable: One timed worked example in Data Structures (General).

Day 4 — Work Object-Oriented Programming (OOP)

  • Spend the session on Object-Oriented Programming (OOP), which DONE by NONE 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 5 — Answer out loud: Computer Science Fundamentals & Data Structures

  • Answer aloud, timed: Explain how a linked list manages dynamic data elements and describe the structure of a node containing data and memory pointers.
  • Answer aloud, timed: Write a program to find the maximum and second maximum numbers in an unsorted array without using built-in sorting algorithms.

Deliverable: Spoken answers to 2 reported Computer Science Fundamentals & Data Structures question(s), under time.

Day 6 — Answer out loud: Object-Oriented Programming & Language Proficiency

  • Answer aloud, timed: Define encapsulation and polymorphism, providing real-world code examples demonstrating their implementation.
  • Answer aloud, timed: How does inheritance differ from composition, and when would you choose one over the other in software architecture?

Deliverable: Spoken answers to 2 reported Object-Oriented Programming & Language Proficiency question(s), under time.

Day 7 — Answer out loud: Computer Networks, Operating Systems & Databases

  • Answer aloud, timed: Walk through the seven layers of the OSI model and explain the function of routing and switching at the network layer.
  • Answer aloud, timed: Explain the key differences between process management and threading within modern operating systems.

Deliverable: Spoken answers to 2 reported Computer Networks, Operating Systems & Databases question(s), under time.

Behavioural preparation

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

Tell me about yourself and walk me through your recent engineering projects and key technical contributions.

Medium · Behavioral, Project Leadership & Domain

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 software engineering projects from initial concept through design to final production releas

Medium · Behavioral, Project Leadership & Domain

How do you manage software engineering projects from initial concept through design to final production release?

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 situation where you received feedback from stakeholders or team members and incorporated it into yo

Medium · Behavioral, Project Leadership & Domain

Describe a situation where you received feedback from stakeholders or team members and incorporated it into your design.

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 do you want to work as a Software Engineer at DONE by NONE?

Medium · Behavioral, Project Leadership & Domain

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?