Based on your JD, this is not a typical MERN interview. It is a Senior Full Stack Engineer (AWS Serverless) interview where they expect you to design production-grade systems.

What Kyndryl is likely testing¶

Looking at the JD, I would estimate the interview focus as:

The keywords Must: TypeScript, NodeJS, Jest, Lambda, API Gateway, Terraform, Docker tell me these technologies will almost certainly come up.

What candidates report about Kyndryl interviews¶

From recent interview experiences shared on Glassdoor and Reddit:

• Most experienced-hire interviews have 2–3 rounds:

• Technical coding + project discussion

• System Design / Architecture

• Managerial or Hiring Manager discussion (sometimes combined) ([Glassdoor][1])

• Multiple candidates mention interviewers spend significant time discussing your own projects, architecture decisions, debugging, cloud experience, and real-world scenarios rather than only algorithm puzzles. ([Glassdoor][2])

• One former employee on Reddit said senior interviews were generally two rounds and emphasized project experience over trick questions, although project assignments may vary because Kyndryl has both development and support engagements. ([Reddit][3])

Most Probable Technical Questions¶

Round 1 (Node.js + TypeScript)¶

Expect questions like:

Node Event Loop¶

Explain Node Event Loop.

Follow-ups

• process.nextTick vs setImmediate
• Promise queue
• Microtask queue
• Event loop phases
• Blocking vs Non-blocking

Streams¶

Difference between

• Readable stream
• Writable stream
• Duplex stream
• Transform stream

When should streams be used?

Cluster vs Worker Threads¶

Difference?

When to use each?

Memory Leak¶

How do you debug a memory leak in Node?

Expected answer

• heap snapshots
• Chrome DevTools
• node --inspect
• clinic.js
• logging
• heapdump

Async¶

Difference

Promise.all()

Promise.allSettled()

Promise.any()

Promise.race()

TypeScript¶

Explain

interface

type

extends

implements

Generics

Utility Types

Partial

Required

Pick

Omit

Record

Readonly

Expect coding questions using Generics.

Coding¶

Write

• debounce
• throttle
• flatten object
• deep clone
• groupBy
• LRU Cache
• Promise implementation
• Retry mechanism

React Questions¶

Very likely

Difference

useEffect

useLayoutEffect

Explain

React.memo

useMemo

useCallback

Virtual DOM

How reconciliation works

Controlled vs uncontrolled components

How to optimize a React application?

Expected answers

• lazy loading
• memoization
• code splitting
• virtualization
• pagination
• React.memo
• useMemo
• useCallback

Redux vs Context API

React rendering lifecycle

AWS Questions (Highest Probability)¶

This JD emphasizes Lambda heavily.

Expect

Lambda¶

Lifecycle

Cold start

Warm start

Execution context

Memory

Timeout

Retries

DLQ

Reserved concurrency

Provisioned concurrency

Why Lambda instead of EC2?

How do you connect Lambda with MongoDB?

How do you reduce Lambda cold start?

API Gateway

REST vs HTTP API

Stages

Throttling

Authorization

Custom authorizer

JWT authorizer

S3

Presigned URL

Multipart upload

Lifecycle policy

IAM

Least privilege

Roles

Policies

Execution role

CloudWatch

Logs

Metrics

Alarms

Tracing

SNS vs SQS

Difference

When to use

FIFO

Visibility timeout

DLQ

Docker Questions¶

Difference

Image

Container

Volume

Bind Mount

Dockerfile optimization

Multi-stage build

Difference

CMD

ENTRYPOINT

How do containers communicate?

Kubernetes¶

Deployment

Pod

ReplicaSet

Service

Ingress

ConfigMap

Secret

Rolling update

Horizontal Pod Autoscaler

Terraform¶

Very likely because JD specifically mentions it.

Questions

Why Infrastructure as Code?

Terraform state

Backend

Workspace

Modules

Variables

Outputs

Lifecycle

Plan

Apply

Destroy

Microservices¶

Expect scenario-based questions.

Example

Design an E-commerce backend.

Explain

Auth

Product

Order

Payment

Notification

Inventory

How do services communicate?

REST

RabbitMQ

Kafka

SQS

How do you maintain consistency?

Saga Pattern

Outbox Pattern

Circuit Breaker

API Gateway benefits

Service Discovery

Database Questions¶

MongoDB

Aggregation

Index

Compound Index

TTL Index

Transactions

Sharding

Replication

SQL

Index

Normalization

Joins

Window Functions

Pagination

Transactions

Isolation Levels

OOP¶

Must prepare

SOLID

Factory

Strategy

Observer

Singleton

Dependency Injection

Repository Pattern

Decorator

Adapter

Builder

Jest¶

Mocking

Spy

Unit test

Integration test

Coverage

beforeEach

afterEach

Mock Express request

Mock MongoDB

REST API¶

PUT vs PATCH

Idempotent

Status codes

JWT Authentication

Refresh Token

Rate limiting

Pagination

Filtering

Versioning

Debugging Questions¶

Very common in senior interviews

"My API is taking 10 seconds."

What will you check?

Expected flow

Load balancer

CloudWatch

Lambda logs

Database

Indexes

Memory

CPU

Network

Redis

Caching

Third-party APIs

Scenario Questions¶

These are very likely.

Scenario 1¶

One Lambda suddenly starts timing out.

How do you debug?

Scenario 2¶

MongoDB CPU becomes 100%.

How will you investigate?

Scenario 3¶

Production API returns 500.

What steps do you take?

Scenario 4¶

React page loads in 9 seconds.

How do you optimize it?

Scenario 5¶

Users report duplicate payments.

How would you fix the architecture?

Coding Questions (Most Asked for 5–10 Years)¶

Prepare these without looking.

• LRU Cache
• Debounce
• Throttle
• Deep Clone
• Flatten Object
• Flatten Array
• Promise Polyfill
• Event Emitter
• Retry with Exponential Backoff
• Merge Intervals
• Group By
• Frequency Counter
• Two Sum
• Longest Substring Without Repeating Characters
• Merge K Sorted Lists
• Binary Tree Traversal (basic)
• BFS
• DFS