Kaseya Software Engineer Interview Guide

The 60-second brief

As a Software Engineer at Kaseya, you will play a pivotal role in designing, building, and scaling the next generation of IT management and security software. Kaseya is a global leader in unified IT and security management software for Managed Service Providers (MSPs) and mid-market enterprises. The systems you build will directly impact millions of endpoints, helping businesses manage their IT infrastructure, automate workflows, and defend against complex cybersecurity threats. The engineering team at Kaseya works on high-impact products that require deep technical expertise in scalability, security, and system reliability. Whether you are optimizing a core backend service, developing cloud-native architectures, or building intuitive frontend experiences, your work will directly influence the stability and security of IT operations worldwide.

This guide is scoped to a Software Engineer candidate at Kaseya.

Focus areas

• Security
• Load Balancing
• JWT (JSON Web Tokens)

The Kaseya interview process

Kaseya 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 role fit.

What to demonstrate

• A call with a recruiter to discuss your background and assess role fit
• Depth in Security

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 Rounds

One or more rigorous technical interviews to evaluate your technical capabilities.

What to demonstrate

• One or more rigorous technical interviews to evaluate your technical capabilities
• Depth in Security

How to prepare

• Answer aloud and timed: Explain the core concepts of Object-Oriented Programming (OOP) and how you apply them in C# or Java.
• Answer aloud and timed: Describe the difference between a process and a thread, particularly in relation to memory allocation in Node.js.

Hiring Manager Review

A final review with a hiring manager or director to assess overall fit.

What to demonstrate

• A final review with a hiring manager or director to assess overall fit
• Depth in Security

How to prepare

• Prepare two projects you led end to end, each with the decision you owned and what it cost.
• Have three questions about the team's roadmap and how success is measured in the first six months.

Where candidates lose points

Master the Textbook Definitions

Do not rely solely on your practical coding experience. Brush up on formal definitions of OOP principles, database normalization, and networking layers, as interviewers frequently look for precise terminology.

Be Ready for Code Reviews

Practice looking at poorly written code and identifying issues. Be prepared to explain why a certain change improves performance, security, or readability.

Proactively Follow Up

The recruitment process at Kaseya can move incredibly fast, but communication gaps can sometimes occur. If you do not hear back within a few days of an interview, proactively reach out to your recruiter for an update.

Questions & practice

What is a binary tree, and what are the time complexities for its common traversal algorithms?

Medium · Computer Science & Core Technical Fundam

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 the difference between a process and a thread, particularly in relation to memory allocation in Node.

Medium · Computer Science & Core Technical Fundam

Describe the difference between a process and a thread, particularly in relation to memory allocation in Node.js.

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 would you write an algorithm to multiply two extremely large numbers containing tens of thousands of digit

Medium · Coding, Problem Solving & Architecture

How would you write an algorithm to multiply two extremely large numbers containing tens of thousands of digits?

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 estimate and forecast project delivery timelines when dealing with ambiguous requirements?

Medium · Behavioral & Team Processes

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 difference between a JOIN and a UNION in SQL, and provide an example of when you would use eac

Medium · Computer Science & Core Technical Fundam

Explain the difference between a JOIN and a UNION in SQL, and provide an example of when you would use each.

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?

Hold a per-tenant active cap against concurrent creates

Hard · write skew · isolation levels · constraints

A tenant on the standard plan may hold at most 50 resources with status='active'. The create handler runs SELECT count(*) FROM resource WHERE tenant_id = $1 AND status = 'active', compares to 50, then inserts. Two creates arrive 3 ms apart on different instances and the tenant lands at 51. Name the anomaly, say whether PostgreSQL 16 READ COMMITTED or REPEATABLE READ prevents it and why, then give an implementation that holds the cap at READ COMMITTED with the exact statements. Finally, say what changes when the cap is 'at most one running export per tenant' on job_run.

Approach

1. Name it: write skew. The two transactions read an overlapping set and write disjoint rows, so there is no row-level conflict for the engine to detect and each commit is individually legal.
2. Rule out the levels precisely. READ COMMITTED takes a fresh snapshot per statement and takes no lock on the counted rows, so both see 49. PostgreSQL's REPEATABLE READ is snapshot isolation: it removes non-repeatable reads and phantoms within the snapshot but still admits write skew, because the anomaly is not a re-read of a changed row, it is a read of a set that a concurrent transaction invalidates. Only SERIALIZABLE closes it, by tracking the read dependency and aborting one transaction with SQLSTATE 40001 — a guarantee that exists only if the application re-runs the whole transaction from the read.
3. Convert the set predicate into a single-row conflict: keep tenant.active_resource_count and run UPDATE tenant SET active_resource_count = active_resource_count + 1 WHERE tenant_id = $1 AND active_resource_count < 50 in the same transaction as the INSERT. Zero affected rows is the cap, returned as 409. The row lock serialises the decision at any isolation level, and contention is bounded to one tenant's row — which is also the fair-scheduling unit, unlike a global counter that would convoy every tenant behind one row.
4. State the cost you just took on: a counter is a second source of truth that can drift, so every path that changes status must adjust it inside the same transaction, and a periodic reconciliation has to exist, with resource_revision as the authority for what the count should have been.

Follow-up

• A resource moves from archived back to active. Which statements change, and what breaks if the counter update and the status change land in different transactions?
• The cap becomes plan-dependent and a plan can change mid-month. Where does the number 50 live, and who reads it?

What is the structure of a JSON Web Token (JWT), and how is it used for secure authentication?

Medium · Computer Science & Core Technical Fundam

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 core concepts of Object-Oriented Programming (OOP) and how you apply them in C# or Java.

Medium · Computer Science & Core Technical Fundam

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?

Implement a basic Load Balancer based on a specific set of routing rules and use cases.

Medium · Coding, Problem Solving & 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?

Design an LRU Cache and explain how you would optimize its read and write operations.

Medium · Coding, Problem Solving & 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 me through how you would design a scalable architecture on AWS or Azure to handle sudden spikes in traffi

Medium · Coding, Problem Solving & Architecture

Walk me through how you would design a scalable architecture on AWS or Azure to handle sudden spikes in traffic.

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?

Review this React-based Todo application: what security vulnerabilities, performance bottlenecks, or refactori

Medium · Coding, Problem Solving & Architecture

Review this React-based Todo application: what security vulnerabilities, performance bottlenecks, or refactoring opportunities do you see?

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?

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 Kaseya candidates report.

Day 1 — Map the Kaseya loop

• Write out the reported sequence: Initial Screening Call, Technical Rounds, Hiring Manager Review.
• 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 Security

• Spend the session on Security, which Kaseya candidates report being tested on.
• Write one worked example in Security and time yourself on it.

Deliverable: One timed worked example in Security.

Day 3 — Work Load Balancing

• Spend the session on Load Balancing, which Kaseya candidates report being tested on.
• Write one worked example in Load Balancing and time yourself on it.

Deliverable: One timed worked example in Load Balancing.

Day 4 — Work JWT (JSON Web Tokens)

• Spend the session on JWT (JSON Web Tokens), which Kaseya candidates report being tested on.
• Write one worked example in JWT (JSON Web Tokens) and time yourself on it.

Deliverable: One timed worked example in JWT (JSON Web Tokens).

Day 5 — Answer out loud: Computer Science & Core Technical Fundamentals

• Answer aloud, timed: What is the structure of a JSON Web Token (JWT), and how is it used for secure authentication?
• Answer aloud, timed: What is a binary tree, and what are the time complexities for its common traversal algorithms?

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

Day 6 — Answer out loud: Coding, Problem Solving & Architecture

• Answer aloud, timed: Implement a basic Load Balancer based on a specific set of routing rules and use cases.
• Answer aloud, timed: Design an LRU Cache and explain how you would optimize its read and write operations.

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

Day 7 — Answer out loud: Behavioral & Team Processes

• Answer aloud, timed: Describe a time when you had to resolve a technical disagreement within your engineering team.
• Answer aloud, timed: How do you estimate and forecast project delivery timelines when dealing with ambiguous requirements?

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

Behavioural preparation

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

Describe a time when you had to resolve a technical disagreement within your engineering team.

Medium · Behavioral & Team Processes

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?

Walk me through your experience with Agile processes, sprint planning, and code review workflows.

Medium · Behavioral & Team Processes

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 you are asked to work with a legacy technology stack that you are not fami

Medium · Behavioral & Team Processes

How do you handle a situation where you are asked to work with a legacy technology stack that you are not familiar with?

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?