java microservice telephonic interview of 10 years experienced

Summary

In this interview, the candidate discusses their experience with microservices architecture and communication methods, including REST and Kafka. They address handling high-throughput scenarios and Java-related topics such as version differences, exceptions, and multi-threading. The candidate also explains key concepts in Java 7 and Java 8, including Comparable vs. Comparator and stream API. They touch on service discovery, service registry, and Spring Boot beans. The interview concludes with a coding challenge to check for anagrams, showcasing the candidate's logical approach to problem-solving.

Takeaways

• 👋 Introduction and current roles and experiences discussed.
• 💻 Discussion about microservices architecture versus monolithic services.
• 🔄 Explanation of service communication using REST template for updates.
• 🔧 Query about the setup and handling of Kafka producer-consumer throughput.
• 📜 Differences between Java 7 Comparable and Comparator explained.
• 🤝 Contract between equals and hash code methods in Java discussed.
• 🔀 Explanation of starvation and deadlock in multi-threading environments.
• ❗️ Difference between compile-time and runtime exceptions in Java.
• 🚫 Explanation of exception handling using throw and throws keywords.
• 🗂 Differences between HashMap, HashTable, and ConcurrentHashMap and their use cases.
• 🌊 Discussion about the use of streams in Java 8 and their advantages over iterators.
• 🔍 Use of service discovery and service registry in applications explained.
• 🔠 Task to check if two strings are anagrams by comparing character counts.
• 🫘 Explanation of the concept of a bean in Spring Boot.

Q & A

What are your current roles and how much experience do you have?

The interviewee is involved in doing both reviews and credit card fixing at a call center. They have experience with these tasks and are proficient in both.

Are you using a microservice architecture or monolithic services?

The interviewee is using microservice architecture.

Can you explain how service communication happens in your current project?

The service communication depends on the type of call. For synchronous calls, they use REST with a REST template for updates and parameters. For asynchronous communication, they use Kafka for event-based messaging.

How would you handle a scenario where your Kafka producer is producing 100 records per second but the consumer is consuming only 20 records per second?

In this scenario, the interviewee would handle the situation by increasing the throughput, likely by adding more consumers or optimizing the existing consumer logic.

What is the difference between Comparable and Comparator in Java?

Comparable has a single method, compareTo, used to define the natural ordering of objects. Comparator, on the other hand, allows multiple comparison methods to define different orderings, often implemented as a functional interface in Java 8 and above.

What is the contract between the equals and hashCode methods in Java?

The contract between equals and hashCode is that if two objects are equal according to the equals method, they must have the same hashCode. However, it is not required for two objects with the same hashCode to be equal according to the equals method.

What is the difference between starvation and deadlock in a multithreading environment?

Starvation occurs when a thread is perpetually denied access to resources, while deadlock is a situation where two or more threads are blocked forever, each waiting on the other to release a resource.

What are some ways to prevent deadlock in a multithreading environment?

To prevent deadlock, one can use techniques like ordering resource acquisition, using a timeout for resource requests, and employing deadlock detection algorithms.

What is the difference between a compile-time exception and a runtime exception in Java?

Compile-time exceptions, also known as checked exceptions, must be handled with try-catch blocks or declared with the throws keyword. Runtime exceptions, or unchecked exceptions, occur during program execution and do not need to be explicitly handled.

What is the difference between the throw and throws keywords in Java?

The throw keyword is used to explicitly throw an exception within a method. The throws keyword is used in a method's signature to declare that the method can throw exceptions of the specified types.

What will happen if a method in a parent class throws a NullPointerException and a method in a child class throws an Exception?

The code will not compile because the child class method cannot throw a broader exception than the parent class method. The exceptions thrown by the child method must be the same or a subclass of the exceptions thrown by the parent method.

What are the differences between HashMap, Hashtable, and ConcurrentHashMap in Java?

HashMap is not synchronized and is suitable for single-threaded environments. Hashtable is synchronized and thread-safe but generally slower. ConcurrentHashMap is designed for concurrent access, providing better performance in multithreaded environments.

Why is the Stream API faster than an iterator in Java?

The Stream API can be faster because it supports parallel processing and allows more optimized operations on data collections.

What is the purpose of service discovery or a service registry in microservices architecture?

Service discovery or service registry is used to register and manage all the services in an application. It helps in locating and distributing client requests to different services, checking the status of services, and managing service instances.

What is a Spring Bean and how is it used?

A Spring Bean is an object managed by the Spring IoC container. It is defined in the configuration file or by using annotations, and the container instantiates, configures, and manages the bean's lifecycle.

Outlines

00:00

😀 Introduction and Experience

The speaker introduces themselves, describing their current roles and technologies they work with. They mention their experience in reviews, credit card fixing, and call center work. They discuss using microservice architecture and the communication methods between different services, including synchronous calls and REST templates.

05:11

🤔 Comparable vs Comparator

The speaker explains the difference between Comparable and Comparator in Java. Comparable has a compareTo method and is used for natural ordering, while Comparator can have multiple methods for customized sorting. They also discuss the contract between equals and hashCode methods, emphasizing consistency in their implementations to avoid errors.

10:14

🧵 Multi-threading: Starvation and Deadlock

The speaker delves into multi-threading, explaining starvation and deadlock. They describe how threads can wait for each other indefinitely, leading to deadlock, and how synchronization blocks can be used to avoid such issues. They also touch upon compile-time vs runtime exceptions and the proper use of throw and throws keywords.

15:16

📝 Java Exceptions and HashMap Variants

The conversation covers the difference between compile-time and runtime exceptions in Java. The speaker also discusses the distinctions between HashMap, Hashtable, and ConcurrentHashMap, including their use cases and performance differences. The benefits of stream processing over iterators in Java 8 are highlighted.

20:17

🔄 Service Discovery and Anagram Logic

The speaker explains service discovery and registry in the context of microservices, using examples of service registry and client requests. They then tackle a coding problem to check if two strings are anagrams, discussing the logic of character count and sorting. The paragraph ends with a brief mention of Spring Boot beans.

Keywords

💡Microservice architecture

A design approach where a single application is composed of multiple small, independent services that communicate with each other. This concept is discussed in the script in the context of how the current project handles service communication and dependencies, contrasting it with monolithic services.

💡Synchronous communication

A type of service communication where a request and response happen in real-time, causing the system to wait for a reply before moving on. The script mentions using REST templates for synchronous calls in the project.

💡Kafka

An open-source stream processing platform used to handle real-time data feeds. The script includes a scenario where the interviewer asks about handling situations where the Kafka producer's rate exceeds the consumer's processing rate.

💡Java 7

An older version of the Java programming language. The script transitions to discussing features and differences between Java 7 and Java 8, specifically mentioning topics like Comparable and Comparator interfaces.

💡Comparable and Comparator

Interfaces in Java used to compare objects. Comparable is used to define the natural ordering of objects, while Comparator is used for custom ordering. These are mentioned in the script when discussing sorting and comparing in Java 7.

💡Equals and hashCode contract

A principle in Java ensuring that if two objects are considered equal using the equals() method, they must have the same hashCode. This is important for correct functionality in hash-based collections. The script references this contract during a discussion on object comparison.

💡Multithreading

A concurrent execution of two or more threads to maximize the utilization of CPU. The script touches on multithreading concepts, including differences between starvation and deadlock, and methods to avoid deadlocks.

💡Deadlock

A state in multithreading where two or more threads are unable to proceed because each is waiting for the other to release resources. The script includes strategies to avoid deadlocks, such as synchronized blocks.

💡Compile-time vs. runtime exception

Compile-time exceptions are checked exceptions that must be handled during compilation, while runtime exceptions are unchecked and occur during the program execution. This distinction is discussed in the context of exception handling in Java.

💡HashMap, Hashtable, ConcurrentHashMap

Different types of maps in Java used for storing key-value pairs. HashMap is not synchronized, Hashtable is synchronized and thread-safe, and ConcurrentHashMap allows concurrent access. The script compares their use cases and performance.

Highlights

Introduction of the interviewee's current roles and technologies.

Discussion about service communication methods in the current project.

Explanation of using synchronous and asynchronous calls with REST template.

Description of Kafka setup and event handling in the project.

Scenario-based question on handling Kafka producer-consumer throughput.

Start of Java questions focusing on versions used.

Difference between Comparable and Comparator in Java 7.

Explanation of the contract between equals and hashCode methods in Java.

Discussion on working in a multithreaded environment and avoiding deadlocks.

Explanation of compile-time versus runtime exceptions in Java.

Difference between throw and throws in exception handling.

Scenario question involving method overriding and exceptions in parent and child classes.

Difference between HashMap, Hashtable, and ConcurrentHashMap.

Features used from Java 8 in the current project, including streams.

Comparison of streams and iterators in Java for parallel processing.

Explanation of service discovery and service registry usage.

Anagram logic and coding task involving string manipulation.

Question on Spring Boot beans and annotations.

Transcripts

ah let's start with the basic

introduction and uh what is your current

roles and how much is experience you

have and a little bit about your current

Technologies

[Music]

sometimes doing both reviews and credit

card fixing added me call center

foreign

are you using my microservice

architecture or monolithic

Services okay can you a little bit uh

explain about how the service

communication happens

into your current project

the different Services

depends on what kind of call we want

like synchronous

so let's say like if it is called

basically we are doing uh like by using

the rest template so we are using the

rest for updates

as part of the parameters and then uh

like that particular services

and if it is

well here we are using like for the

communication we are using that

let's call it

okay so have you set up that Kafka or it

all set up by the another person

the more our team used to work the

functionality we are working basically

it is a synchronous call we are saying

so I am more profitable in that but yes

we are using that

event

if new event they are adding so they are

adding into the XML files

correct in details because

okay okay

fine so like I have one scenario for the

Kafka uh my producer is producing 100

records per second

but my consumer is consuming 20 record

per second

so how you will handle this scenario

like in some case it will be

a full queue and you will not able to

push the records into your queue so what

you will do in this scenario

how will you how you will increase the

throughput

s

okay okay fine

so let's start with the Java questions

currently which Java version you are

using

okay Jared let's start with the Jazz

some job seven questions first and then

we will move to the javasa it so in a

Java 7 we have comparable and

comparative what is the difference

between those

is having highest incomparable

comparabilities compared to method is

there and Main comparator we are we are

having a second by expression which of

the methods are there in a comparable

method only is available English to

interfaces and actually even we can send

Java it we can say it time with the

functional interface also but in

compatibility is the method is available

okay okay

yeah yeah okay what so like uh an

incomparable comparator we are using

equals methods and uh hash codes also so

what is the contract between equals and

hash code method

in Java

is

if we can select if the first method we

are doing the uh let's say the

temperature right by using first method

and if the output is like whatever

output it is given from the equals

method the hasbode method also is going

to give us the same but the contract

like the Y Square size Mark correct like

it can be different so we can say equals

method we can return value and password

return value will be same if it is like

but if if the has per value is returning

something

method

okay okay fine

so in a uh

uh have you work in a multi-theory

environment

project

s

okay so what is the difference between

starvation and date lock

okay

we have to create some more threads and

they are waiting for each other to get

the object Club let's say I have foreign

[Music]

[Music]

and

and we can cover it like if you want to

Google it um like to reserve it

basically we can use this uh using the

synchronized block or synchronization

paper basically we can play positive

blog so that only one third will execute

once the execution

get released then another thread we can

give it like we can add another checking

status execution

foreign

yeah yeah fine no problem so while

you're giving answers you told that like

a star which uh deadlock can be avoided

so what are the like what are the ways

we implement or we

uh follow so that we will not able to

get into deadlock situation

so can you give some examples like in

your projects which you guys follow or

followed

we can keep

we can call those methods like in in the

living we can select application between

threads we can keep it in some way

things States and we can call that

notify notify all method at all or we

can basically if we are going to do

because before having a synchronization

we can say this is a straight set so

that only one thread will be like able

to access that particular lock of that

object there

okay so what is the okay thanks

so what is the difference between a

compile time

exception Android time exception

second exception

this basically there's two exceptions

yeah it's it's the part of exception

class so that definition we can say it

is uh it will be used to get it in the

compiled time and we we will be able to

test it or we can we can handle this

exception so that like well writing

before we can give the cash flow or

close keyword and then we can use it and

we can handle that exercise but runtime

exceptions basically we will get that

for runtime only so that like we can say

something like we have to open whenever

we are writing that code let's say uh

array index out of boundary and that

kind of exception only used questions

so in that case we have whenever we are

writing that code we have to take care

of the uh like exercise

so you can

handle it in the foreign

yeah

okay

we are writing our like custom

exceptions we can say so those exception

candles we can uh keep it as part of the

objectives

okay so while implementing or writing

the exception code you we use throw and

Truth what is the difference between

throw and those

of course basically we are using a

startup first method uh

signature itself

whenever we want to throw that

exceptions we can

okay so suppose I have class A which is

my parent and I have class B which is my

child class

so in parent class I have a method

display over the display method I am

throwing the exception

uh

null pointer exception okay

close null pointer exception so

and Below there is one method in a child

class same method which is X throwing

the exception throwing

exception okay

so will this class compile or will

or it will throw the runtime exception

so that is

showing that except something like the

main line yeah

it is like super self yes

so

I think now it will not allow us because

we can we can give in the Surplus only

like the uh let's start back at the

final Foundation if we are showing the

exceptions in class a method and we are

using some other exceptions in the class

three methods then I think it will allow

okay yeah right

type of exceptional it will not be it

will not Allah

okay great

uh we have a hash map has

cable and concurrent hashmah so what is

the difference between these three when

we use and when

which is the faster from these three and

what is the use cases of these three

okay as you have Snapchat has not

basically we are using uh

it

is like

I can make we can make it as simple

by using the synchronized math method

confident has not possibilities like uh

it is getting used for the single thread

environment

yeah yeah got it okay so like uh how

much you're not expense like your legs

move to the

so from java it like uh which are the

features you have used in your current

project

foreign

okay so have you uh like I used a stream

okay so why stream is faster than

iterator

like it will do uh what to select it is

like we are we used to get the output

also as a stream type basically so we

can say based on the parallel processing

it is

of so how much iron for experience you

have in a

um

okay so what is the use of service

Discovery or Services history

basically we are using this service

registry we can sell it to register all

of our services like whatever Services

we are using as part of application we

can register there so we can unless they

like we are using something like example

the service resistance you requests

of client is

located

and distribute certificates to the

different Services which is available in

the service resolution so we can even

take in the service registry the how

many uh services are available already

is in the uh which state like the status

of the services like it is active or not

we used to get it and uh

as a service registry we can use like we

have producer Factory we can like we are

going into the apartment can help and we

can give in the service track like

enable uh

um

okay thanks okay so like uh do you have

any coding editor open Let's uh

okay can you share so I will be giving

one small example uh

I have one program like uh let's take I

am write a string like a RM programmer

then there is one more string

programmer I am

so you have to tell

uh is it an anagram or not okay

so

you know what is mean by another

all right yes I think it is it should be

like having the same characters

okay and same count of the character

many characters and same count yes

uh you can tell me logic and then start

or because we have a listen

think on that

um

I can do here one thing like if first

I'll check the length

so what I can do I can keep it this

thing to some character array

in this one also I can keep it into some

character array when I can sort that

value after using something like let's

say uh for that particular character

arrive here it is now it's a character

that I am having all those characters

sort with screen character then I can

use one more foreign

okay

so

uh I have like uh some questions from

the spring boot like in Spring boot we

have a

string and spring mode okay we have a

bean okay so what is mean by b

I like The annotation chip we are using

or

like we have to do the foreign

oh great