Interview guides · Kyndryl

Kyndryl Software Engineer Interview Guide

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

The 60-second brief

As a Software Engineer at Kyndryl, you are at the heart of managing and modernizing the world’s most critical technology infrastructure. You will be responsible for designing, developing, and deploying robust software solutions that empower our global clients to navigate their digital transformation journeys. This role is not just about writing code; it is about building scalable, secure, and resilient systems that keep enterprise-grade environments running smoothly. You will contribute to complex projects that span cloud computing, mainframe modernization, data management, and automation. Working at the intersection of legacy stability and modern agility, you will solve real-world problems that have a direct impact on business operations.

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

Focus areas

Python (basics)
SQL (queries)
Problem-solving skills

The Kyndryl interview process

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

Initial Screening

The process begins with an initial screening to assess candidates' qualifications.

What to demonstrate

The process begins with an initial screening to assess candidates' qualifications
Depth in Python (basics)

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 Evaluations

Candidates undergo deeper technical evaluations to assess their technical baseline.

What to demonstrate

Candidates undergo deeper technical evaluations to assess their technical baseline
Depth in Python (basics)

How to prepare

Answer aloud and timed: How do you find the maximum element in an array?
Answer aloud and timed: Explain the difference between SQL and NoSQL databases and when to use each.

Online Assessments

Depending on the location and business unit, candidates may encounter online assessments.

What to demonstrate

Depending on the location and business unit, candidates may encounter online assessments
Depth in Python (basics)

How to prepare

Answer aloud and timed: What is your approach to Redux state management in a React application?
Answer aloud and timed: Can you walk me through a technical challenge you faced in a recent project and how you resolved it?

Group Discussions

Candidates may participate in group discussions as part of the interview process.

What to demonstrate

Candidates may participate in group discussions as part of the interview process
Depth in Python (basics)

How to prepare

Answer aloud and timed: Describe the tools and frameworks you used in your most recent project and why they were chosen.
Answer aloud and timed: How do you ensure your code follows coding standards and best practices?

Where candidates lose points

Own your resume

Every project listed on your resume is fair game. Be prepared to explain the tools used, the challenges faced, and the specific impact of your work in granular detail.

Master the basics

Don't overlook fundamentals like OS, Networking, and OOPS. Many candidates focus too much on advanced frameworks and miss simple questions about these foundational topics.

Prepare for the English Assessment

For many roles, the initial hurdle is an English proficiency test. It is often speed-based, so practice your grammar and vocabulary to ensure you can move quickly without sacrificing accuracy.

Some candidates report that they are not always notified of their status in a timely manner

If you haven't heard back after a reasonable period, it is acceptable to reach out to your HR contact for an update.

Questions & practice

Explain the core principles of Object-Oriented Programming (OOP) and how you apply them in your projects.

Medium · Technical Foundations and Coding

Approach

Restate the input: its shape, its size, and what is guaranteed about it.
Name the brute-force solution and its complexity before improving on it.
Choose the data structure from the access pattern, not from familiarity.
State the target complexity and say which constraint rules the naive version out.

Follow-up

How does this change if the input no longer fits in memory?
What is the worst case, and how likely is it on real data?

Describe how you would handle File Operations in your preferred programming language.

Medium · Technical Foundations and Coding

Approach

Restate the input: its shape, its size, and what is guaranteed about it.
Name the brute-force solution and its complexity before improving on it.
Choose the data structure from the access pattern, not from familiarity.
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 find the maximum element in an array?

Medium · Technical Foundations and Coding

Approach

Restate the input: its shape, its size, and what is guaranteed about it.
Name the brute-force solution and its complexity before improving on it.
Choose the data structure from the access pattern, not from familiarity.
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 is your approach to Redux state management in a React application?

Medium · Technical Foundations and Coding

Approach

Restate the input: its shape, its size, and what is guaranteed about it.
Name the brute-force solution and its complexity before improving on it.
Choose the data structure from the access pattern, not from familiarity.
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 SQL and NoSQL databases and when to use each.

Medium · Technical Foundations and Coding

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?

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

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.
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.
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.
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?

Can you walk me through a technical challenge you faced in a recent project and how you resolved it?

Medium · Project-Based Discussions

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 tools and frameworks you used in your most recent project and why they were chosen.

Medium · Project-Based Discussions

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 ensure your code follows coding standards and best practices?

Medium · Project-Based Discussions

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?

Explain the architecture of your project and how it interacts with external systems or APIs.

Medium · Project-Based Discussions

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?

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

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.
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.
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.
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 Kyndryl candidates report.

Day 1 — Map the Kyndryl loop

Write out the reported sequence: Initial Screening, Technical Evaluations, Online Assessments, Group 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 Python (basics)

Spend the session on Python (basics), which Kyndryl candidates report being tested on.
Write one worked example in Python (basics) and time yourself on it.

Deliverable: One timed worked example in Python (basics).

Day 3 — Work SQL (queries)

Spend the session on SQL (queries), which Kyndryl candidates report being tested on.
Write one worked example in SQL (queries) and time yourself on it.

Deliverable: One timed worked example in SQL (queries).

Day 4 — Work Problem-solving skills

Spend the session on Problem-solving skills, which Kyndryl candidates report being tested on.
Write one worked example in Problem-solving skills and time yourself on it.

Deliverable: One timed worked example in Problem-solving skills.

Day 5 — Answer out loud: Technical Foundations and Coding

Answer aloud, timed: Explain the core principles of Object-Oriented Programming (OOP) and how you apply them in your projects.
Answer aloud, timed: Describe how you would handle File Operations in your preferred programming language.

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

Day 6 — Answer out loud: Project-Based Discussions

Answer aloud, timed: Can you walk me through a technical challenge you faced in a recent project and how you resolved it?
Answer aloud, timed: Describe the tools and frameworks you used in your most recent project and why they were chosen.

Deliverable: Spoken answers to 2 reported Project-Based Discussions question(s), under time.

Day 7 — Answer out loud: Behavioral and Role Fit

Answer aloud, timed: Tell me about yourself and your professional journey.
Answer aloud, timed: Why are you interested in joining Kyndryl?

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