At Daikin, a Software Engineer plays a vital role in transforming global climate control and industrial manufacturing through intelligent technology. As a world leader in HVAC/R (Heating, Ventilation, Air Conditioning, and Refrigeration) solutions, Daikin relies on software engineering to power everything from embedded unit controllers and smart edge devices to cloud telemetry platforms, automated manufacturing systems, and enterprise tools. In this position, your work directly impacts product efficiency, environmental sustainability, and end-user comfort. Whether you are developing low-level C/C++ firmware for commercial chillers, engineering cloud services to analyze sensor streams in real time, or optimizing complex database systems that support global operations, your code touches critical infrastructure. You will collaborate closely with mechanical engineers, product managers, quality teams, and factory personnel across major facilities in North America, Europe, and Asia. The engineering ecosystem at Daikin balances traditional industrial reliability with modern digital transformation. Candidates who thrive here possess strong foundational engineering principles, a rigorous approach to system architecture, and the communication skills required to bridge the gap between software logic and physical hardware.
Phone Screening
reportedInitial call conducted by HR to assess candidate fit and discuss the role.
What to demonstrate
- Initial call conducted by HR to assess candidate fit and discuss the role
- Depth in Software Engineering Fundamentals
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
reportedSeries of interviews focusing on technical knowledge and problem-solving skills.
What to demonstrate
- Series of interviews focusing on technical knowledge and problem-solving skills
- Depth in Software Engineering Fundamentals
How to prepare
- Answer aloud and timed: Write a complex SQL query to extract and aggregate operational telemetry data across relational tables.
- Answer aloud and timed: Explain the key differences between synchronous and asynchronous execution in cloud services.
Behavioral Interviews
reportedInterviews that evaluate past experiences and cultural fit within the team.
What to demonstrate
- Interviews that evaluate past experiences and cultural fit within the team
- Depth in Software Engineering Fundamentals
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 interviews above and write down what you would ask to confirm before it.
Stakeholder Engagement
reportedEngagement with multiple stakeholders, including hiring managers and team members.
What to demonstrate
- Engagement with multiple stakeholders
- Including hiring managers and team members
How to prepare
- Answer aloud and timed: How would you design a software feedback loop to regulate temperature and airflow in a commercial unit?
- Answer aloud and timed: What factors count toward calculating heat load and deciding unit positioning for optimal climate control?
PracHub editorial advice for the preparation topics above.
Prepare for Cognitive & Aptitude Assessments
Be ready for timed numerical, logical, and verbal reasoning tests. Practice basic mental math and logic puzzles under time pressure before taking the assessment.
Emphasize Practical Application
When describing past projects, highlight real-world constraints—such as execution time, memory usage, network reliability, or hardware safety—rather than purely theoretical concepts.
Demonstrate Respect for Manufacturing Operations
Highlight experience where you successfully collaborated with non-software teams, such as production crews, technicians, or quality control managers.
Choose a category, try a prompt, then open its approach, worked solution or follow-up when you need it.
How do you handle memory management and pointers in C/C++ when developing resource-constrained software?
How do you handle memory management and pointers in C/C++ when developing resource-constrained software?
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?
Explain the key differences between synchronous and asynchronous execution in cloud services.
Explain the key differences between synchronous and asynchronous execution in cloud services.
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?
Identify the heaviest tenants in a five-minute window under memory pressure
The edge service handles about 3,000 requests per second across roughly 50,000 tenants, peaking near 9,000. Expose the 50 heaviest tenants by request count over the trailing five minutes so limits can be tightened before one tenant's backfill starves the fleet. You may not retain five minutes of raw records. Give the exact solution and its memory, then the bounded-memory approximation with its error stated as a formula, and say which you would ship and at what tenant cardinality that choice changes.
Approach
- Do the exact version first, because it is affordable at this cardinality: a ring of 300 one-second counters per tenant, advanced lazily, is 1,200 bytes of counters per tenant and roughly 60 to 90 MB for 50,000 tenants with overhead. Carry a running total and subtract the bucket you overwrite so a window read is O(1) rather than 300 adds.
- Extract the top 50 with a size-k min-heap over the tenant sums: O(d log k) for d tenants, against O(d log d) to sort them all. Maintaining the heap continuously instead of on query requires a tenant-to-heap-index map, because incrementing a count already inside the heap means sifting from a known position, and without that map you rebuild the heap on every request.
- State the approximation precisely rather than gesturing at sketches. Misra-Gries with m counters retains every item whose true count exceeds N/(m+1), and each retained count underestimates the truth by at most N/(m+1). With m = 1,000 and N = 900,000 requests in the window the error is roughly 900 requests, which is fine for spotting a tenant sending 50,000 and useless for ranking two tenants 200 apart.
- Say what breaks when the window slides: Misra-Gries and Space-Saving are insert-only and cannot be decremented as records age out. The workable construction is one summary per sub-window, say ten seconds, with 30 summaries merged at query time, and the merged error is the sum of the per-summary errors, so the bound degrades linearly in the number of sub-windows.
Follow-up
- The heaviest tenant is heavy because of one export job rather than user traffic. Should the limiter treat those as the same tenant?
- Two tenants sit tied at the boundary of the top 50. Does your answer flap, and does the flapping matter?
Write a complex SQL query to extract and aggregate operational telemetry data across relational tables.
Write a complex SQL query to extract and aggregate operational telemetry data across relational tables.
Approach
- Name the grain you start from and join outward from it.
- Check whether any join is one-to-many before aggregating, or the sums inflate.
- Say which index the query would use, and what makes it unusable.
- 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
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
- 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.
- 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.
- 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.
- 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?
Explain Object-Oriented Programming (OOP) concepts based on a provided UML class diagram.
Explain Object-Oriented Programming (OOP) concepts based on a provided UML class diagram.
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 design software to maintain system stability during sensor signal dropouts or hardware faults?
How do you design software to maintain system stability during sensor signal dropouts or hardware faults?
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 basic refrigeration cycle and explain how software controls expansion valves and compressors.
Describe the basic refrigeration cycle and explain how software controls expansion valves and compressors.
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?
How would you design a software feedback loop to regulate temperature and airflow in a commercial unit?
How would you design a software feedback loop to regulate temperature and airflow in a commercial unit?
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 factors count toward calculating heat load and deciding unit positioning for optimal climate control?
What factors count toward calculating heat load and deciding unit positioning for optimal climate control?
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?
How do microcontrollers read data from digital and analog sensors like relays and thermistors?
How do microcontrollers read data from digital and analog sensors like relays and thermistors?
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?
Walk us through how you would architect a control application for a screw compressor or chiller unit.
Walk us through how you would architect a control application for a screw compressor or chiller unit.
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?
How would you design an end-to-end telemetry system that streams diagnostic data from thousands of connected H
How would you design an end-to-end telemetry system that streams diagnostic data from thousands of connected HVAC units to the cloud?
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?
How do you optimize database queries when processing large volumes of marketing or performance analytics?
How do you optimize database queries when processing large volumes of marketing or performance analytics?
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?
How do you approach designing system interfaces when working with incomplete software requirements?
How do you approach designing system interfaces when working with incomplete software requirements?
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 perform component selection and system balancing for an integrated hardware-software platform
Describe how you perform component selection and system balancing for an integrated hardware-software platform.
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?
Walk through your step-by-step process for debugging a critical intermittent issue in a production control sys
Walk through your step-by-step process for debugging a critical intermittent issue in a production control system.
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 Daikin candidates report.
Prepare, practise & reflect
One practical outcome each day. Spend longer where you need it.
0 / 7 done01Map the Daikin loop
- Write out the reported sequence: Phone Screening, Technical Interviews, Behavioral Interviews, Stakeholder Engagement.
- 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.
02Work Software Engineering Fundamentals
- Spend the session on Software Engineering Fundamentals, which Daikin candidates report being tested on.
- Write one worked example in Software Engineering Fundamentals and time yourself on it.
Deliverable: One timed worked example in Software Engineering Fundamentals.
03Work Technical Interview Preparation
- Spend the session on Technical Interview Preparation, which Daikin candidates report being tested on.
- Write one worked example in Technical Interview Preparation and time yourself on it.
Deliverable: One timed worked example in Technical Interview Preparation.
04Work Manufacturing Process Knowledge (Domain)
- Spend the session on Manufacturing Process Knowledge (Domain), which Daikin candidates report being tested on.
- Write one worked example in Manufacturing Process Knowledge (Domain) and time yourself on it.
Deliverable: One timed worked example in Manufacturing Process Knowledge (Domain).
05Answer out loud: Technical & Software Fundamentals
- Answer aloud, timed: Explain Object-Oriented Programming (OOP) concepts based on a provided UML class diagram.
- Answer aloud, timed: How do you handle memory management and pointers in C/C++ when developing resource-constrained software?
Deliverable: Spoken answers to 2 reported Technical & Software Fundamentals question(s), under time.
06Answer out loud: HVAC & Domain Integration
- Answer aloud, timed: Describe the basic refrigeration cycle and explain how software controls expansion valves and compressors.
- Answer aloud, timed: How would you design a software feedback loop to regulate temperature and airflow in a commercial unit?
Deliverable: Spoken answers to 2 reported HVAC & Domain Integration question(s), under time.
07Answer out loud: Problem-Solving & System Design
- Answer aloud, timed: How would you design an end-to-end telemetry system that streams diagnostic data from thousands of connected HVAC units to the cloud?
- Answer aloud, timed: Walk through your step-by-step process for debugging a critical intermittent issue in a production control system.
Deliverable: Spoken answers to 2 reported Problem-Solving & System Design 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 situation where you had to work directly with a manufacturing or production crew to resolve an issu
Describe a situation where you had to work directly with a manufacturing or production crew to resolve an issue.
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 respond when a project timeline is compressed or critical deadlines are running late?
How do you respond when a project timeline is compressed or critical deadlines are running late?
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?
Give an example of a time you had to explain a complex technical concept to a non-technical stakeholder.
Give an example of a time you had to explain a complex technical concept to a non-technical stakeholder.
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 disagreements with team members or senior leadership regarding system architecture?
How do you handle disagreements with team members or senior leadership regarding system architecture?
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 yourself in three words and explain why you chose to apply to Daikin.
Describe yourself in three words and explain why you chose to apply to Daikin.
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 situation where you had to work directly with a manufacturing or production crew to resolve an issue.
- 02
How do you respond when a project timeline is compressed or critical deadlines are running late?
- 03
Give an example of a time you had to explain a complex technical concept to a non-technical stakeholder.
- 04
How do you handle disagreements with team members or senior leadership regarding system architecture?
How difficult is the technical evaluation at Daikin?
The technical difficulty is generally moderate to challenging, depending on the focus area. Embedded and control roles dive deeply into C/C++ memory management, logic design, and hardware interaction, while enterprise roles focus heavily on system architecture, database design, and SQL.
Daikin Software Engineer candidate reports ↗What should I expect during the automated video screen?
The video screening stage presents automated questions on screen, typically allowing 1 to 2 minutes per answer with limited retries. Practice speaking concisely, maintain eye contact with your camera, and structure your responses clearly using the STAR method (Situation, Task, Action, Result). Automated video interviews have strict time limits per question. Plan your answers to be concise so your recording does not cut off mid-sentence.
Daikin Software Engineer candidate reports ↗Is prior HVAC experience required for Software Engineer roles?
While prior HVAC or refrigeration experience is a distinct advantage—especially for controls and application engineering roles—it is not strictly mandatory for all positions. Candidates with strong software engineering fundamentals and a willingness to learn domain concepts can succeed.
Daikin Software Engineer candidate reports ↗What is the purpose of the plant tour during on-site interviews?
The plant or laboratory tour allows the hiring team to evaluate your interest in physical manufacturing and gauge how comfortably you engage with the operational environment. It also gives you a clear look at where your software will be deployed and tested.
Daikin Software Engineer candidate reports ↗How long does the hiring process usually take from start to finish?
The entire process generally takes between three to six weeks. Timelines vary based on regional hiring schedules, assessment completion, and scheduling panel interviews across cross-functional team members.
Daikin Software Engineer candidate reports ↗What topics does Daikin test in interviews?
Daikin interviews most often cover Stakeholder Management, Requirements Gathering, Inductive Reasoning, Stakeholder Communication, and Behavioral Interviewing. The exact emphasis depends on the specific role you apply for.
Daikin 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.
- 01Daikin 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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