Explain what happens with React's "virtual DOM" whenever render fires, and why it's so great.

Whenever React renders the component tree, it looks for changes from the virtual DOM to the actual DOM. If there are changes, it will updat...

What are Synthetic events?

In order to ensure events have consistent properties across different browsers, React wraps the browser's native events into "synt...

How can you access something inside state?

this.state._____ inside JSX {} inside render if this.state = { name: "Nick" }; then... {this.state.name}

How can you set state initially (within the constructor() method)?

constructor() { super(); this.state = { name: "Vikas" }; }

What is the primary type in React? It's a light, stateless, immutable, virtual rep of a DOM element?


What is one of the core types in React?


How to assign form values to properties on the component object?

We can use refs to assign form values to properties on the component object. input: dom element passed in the function <input ref={(in...

How you will update a Component's state?

We update state by calling this.setState(), this causes our component to re-render. this.setState({showComments:true}) Will only update ...

What is a state? How to use state?

State handles data changes. State is a JavaScript object that lives inside each component. We can access it via this.state. In React we mod...

Why do we capitalize components?

Because they're a constructor. It is not a rendered DOM element YET, it just has the capacity to render out a DOM element whenever we p...

What is the module loader of choice for React developers?


What's a difference between a DOM object and a virtual DOM object?

A virtual DOM object can update much faster than a regular DOM object. A virtual DOM object can't directly affect HTML. A virtual D...

What is virtual DOM diffing?

When Component rendering for the second time Virtual DOM checks what element get changed and print the changed element to the page, other e...

How Virtual DOM Works?

When you render a JSX element, every single virtual DOM object gets updated.This sounds incredibly inefficient, but the cost is insignifica...

Explain Virtual DOM?

In React, for every DOM object, there is a corresponding "virtual DOM object." A virtual DOM object is a representation of a DOM ...

Explain what is Prop?

When we use our defined components, we can add attributes called props. These attributes are available in our component as this.props and c...

In JSX why you can't use "class" word?

In JSX, you can't use the word class. You have to use className instead because JSX gets translated into JavaScript, and class is a res...

A JSX expression must have exactly how many outermost elements?

It must have exactly one outermost element. var paragraphs = ( <div id="i-am-the-outermost-element"> <p>I am a par...

If a JSX expression takes up more than one line, what should you do?

You should wrap the multi-line JSX expression in parentheses. This looks strange at first, but you get used to it: ( <a href="ht...

Can you nest JSX elements inside of other JSX elements?

Yes! You can nest JSX elements just like you can do with HTML elements.

Can Browsers read JSX? If not, Why?

JSX is not valid JavaScript. Web browsers can't read it! If a JavaScript file contains JSX code, then that file will have to be compile...

Write small code that will render a JSX expression?

ReactDOM.render(<h1>Hello world</h1>, document.getElementById('app'));

What do you understand by JSX? Explain it.

JSX is a syntax extension for JavaScript. Basically HTML that goes into a js file to be compiled into real HTML. A JSX expression must have...

Is it true or false that ReactJS is an MVC based framework?


What two things do you need to pull in on the main index.html file? ReactJS

React and JSX Transformer <script type="text/javascript" src="https://cdnjs.cloudflare.com/ajax/libs/react/0.13.1/react....

What are the advantages/benefits and limitations of React?

Following are the advantages/benefits and limitations of React Advantages/benefits: ReactJS can be used on client and server side too. ...

What is ReactJS?

React.js is a JavaScript library developed by engineers at Facebook for building user interfaces. ReactJS allows us to create reusable UI c...

How you will connect to JSON Data in Dundas BI

Click here for answers

What are the benefits of Animated Data Transitions?

Improves perception of changes between statistical data graphics Helps tell the story of data changes through time in a meaningful way ...

What is the difference between Dundas Dashboard and Dundas BI?

Dundas BI is a completely separate product with a different codebase and an expanded scope, focusing on self-serve business intelligence, f...

Explain the Key Features of Dundas BI?

Following are the Key Features and Benefits of Dundas BI Self-Serve Business Intelligence: Dundas BI gives you the ability to create you...

Explain what is Dundas BI?

Dundas BI is a state-of-the-art business intelligence platform for building and using interactive dashboards, reports, scorecards, and mor...

What is Power BI Desktop?

Power BI Desktop is a free desktop application you can install right on your own computer. Power BI Desktop works cohesively with the Power...

What’s the difference between Power BI and Power BI Pro?

Power BI provides all sorts of features to help you get started exploring data in a whole new way. Power BI Pro provides all of the same gr...

Top 60 AWS DevOps Real Time Interview Questions Answers

Here we come with most growing technology related interview questions, the technology is known as Amazon Virtual Private Cloud, we are post...

What is Puppet?

Puppet is a Configuration Management tool that is used for deploying, configuring and managing servers. It performs the following functions...

What is Scrum?

Scrum is a simple framework for effective team collaboration on complex projects. Scrum provides a small set of rules that create "jus...

What is Build Automation?

Tools or frameworks that allow source code to be automatically compiled into releasable binaries. Usually includes code-level unit testing ...

What do you understand by LXC?

LXC - (LinuX Container) is an operating system-level virtualization method that allows multiple isolated Linux systems to run as a single h...

Explain what do you understand by A3 Problem Solving?

A structured problem‐solving approach that uses a lean tool called the A3 Problem‐Solving Report. The term "A3" represents the pa...

Explain Git?

Git is a free, open source distributed version control system tool designed to handle everything from small to very large projects with spe...

What do you understand by term Provisioning in DevOps?

Provisioning is the process of preparing new systems for users (in a Continuous Delivery scenario, typically development or test teams). Th...

What is Dark Launch?

It is a go-live strategy in which code implementing new features is released to a subset of the production environment but is not visibly, ...

What do you understand by NGINX?

NGINX is open source software for web serving, reverse proxying, caching, load balancing, media streaming, and more. ... In addition to its...

What do you understand by Acceptance Testing?

Acceptance Testing is typically high-level testing of the entire system carried out to determine whether the overall quality of both new an...

What is Chef?

Chef is an automation tool that provides a way to define infrastructure as code. Infrastructure as code (IAC) simply means that managing in...

Deploy vs. Release in DevOps? What do you understand by these two terms?

You can deploy code to production without releasing Release is to make functionality available to end users

What are the Principles of DevOps?

Collaboration Breakdown the barriers Work as one team end to end Treat Infrastructure as code Support business and IT agility Autom...

What are the Disadvantages of using DevOps?

1. Lack of resources (Developers) 2. Developer are so costly due to lack of resources 3. Difficult to hire good DevOps developer. 4. Dev...

What is Elastic Block Store?

Elastic Block Store aka EBS is a type of block storage system that provides persistent block storage volumes for use with EC2.

What is Software-as-a-Service?

It is a software distribution model where applications are hosted by a vendor and made available to customers over the Internet

How do you practice DevOps?

By using automated testing, continuous integration, continuous delivery and automated infrastructure.

What do you understand by Agile Software Development?

It is a software development methods in which requirements and solutions evolve through collaboration between self-organizing, cross-functi...

What are the steps to build a custom VPC?

Below are the steps of build a custome VPC: 1. Create a VPC 2. Create subnets 3. Create an internet gateway (IGW) 4. Attach the new IG...

What are the AWS Services for DevOps?

AWS CodeCommit: AWS CodeCommit is a fully-managed source control service that makes it easy for companies to host secure and highly sca...

What do you understand by this diagram?

Ans: This diagram is showing DevOps as the intersection of development (software engineering), technology operations and quality as...

DevOps focuses on 4 primary areas within IT?

1. Culture. 2. Organization (style including roles). 3. Processes. 4. Tools.

What are the Advantage/Benefits of using AWS for DevOps? Why use AWS for DevOps?

AWS DevOps Interview Question: What are the Advantage/Benefits of using AWS for DevOps? Why use AWS for DevOps? Ans: Below are the Beni...

What are the Advantage/Benefits of DevOps? AWS DevOps Interview Questions

Speed: Move at high velocity so you can innovate for customers faster, adapt to changing markets better, and grow more efficient at dr...

What is DevOps? AWS DevOps Interview Questions Answers

DevOps is the combination of cultural philosophies, practices, and tools that increases an organization’s ability to deliver applications a...

Top 95 AWS VPC Interview Questions Answers PDF

Here we come with most growing technology related interview questions, the technology is known as Amazon Virtual Private Cloud, Today is 18...

Can Amazon EC2 instances within a VPC communicate with Amazon S3?

Yes. There are multiple options for your resources within a VPC to communicate with Amazon S3. You can use VPC Endpoint for S3, which makes...

How do you disable NAT-T on my connection?

You will need to disable NAT-T on your device. If you don’t plan on using NAT-T and it is not disabled on your device, we will attempt to e...

How do you assign private IP addresses to Amazon EC2 instances within a VPC?

When you launch an Amazon EC2 instance within a VPC, you may optionally specify the primary private IP address for the instance. If you do ...

Is there a limit on how large or small a subnet can be?

The minimum size of a subnet is a /28 (or 14 IP addresses.) for IPv4. Subnets cannot be larger than the VPC in which they are created.

How many subnets can I create per VPC?

Currently you can create 200 subnets per VPC. If you would like to create more, please submit a case at the support center.

Can you change a VPC's size?

No. To change the size of a VPC you must terminate your existing VPC and create a new one.

What defines billable VPN connection-hours?

VPN connection-hours are billed for any time your VPN connections are in the "available" state. You can determine the state of a ...

Can you assign multiple IP addresses to an instance?

Yes. You can assign one or more secondary private IP addresses to an Elastic Network Interface or an EC2 instance in Amazon VPC. The number...

Can you assign any IP address to an instance?

You can assign any IP address to your instance as long as it is: Part of the associated subnet's IP address range Not reserved by A...

What IP address ranges are assigned to a default VPC?

Default VPCs are assigned a CIDR range of Default subnets within a default VPC are assigned /20 netblocks within the VPC CID...

How do you assign IP address ranges to VPCs?

You assign a single Classless Internet Domain Routing (CIDR) IP address block when you create a VPC. Subnets within a VPC are addressed fro...

What IP address do you use for your CGW address?

You will use the public IP address of your NAT device.

Can you NAT your CGW behind a router or firewall?

Yes, you will need to enable NAT-T and open UDP port 4500 on your NAT device.

Are there any VPN connection throughput limitations?

Amazon does not enforce any restrictions on VPN throughput. However, other factors, such as the cryptographic capability of your customer g...

How do I connect a VPC to my corporate datacenter?

Establishing a hardware VPN connection between your existing network and Amazon VPC allows you to interact with Amazon EC2 instances within...

What tools are available to me to help troubleshoot my Hardware VPN configuration?

The DescribeVPNConnection API displays the status of the VPN connection, including the state ("up"/"down") of each VPN ...

Does ClassicLink affect the access control between the EC2-Classic instance, and other instances that are in the EC2-Classic platform?

ClassicLink does not change the access control defined for an EC2-Classic instance through its existing Security Groups from the EC2-Classi...

Can traffic from an EC2-Classic instance travel through the Amazon VPC and egress through the Internet gateway, virtual private gateway, or to peered VPCs?

Traffic from an EC2-Classic instance can only be routed to private IP addresses within the VPC. They will not be routed to any destinations...

Name any VPCs for which you cannot enable ClassicLink?

ClassicLink cannot be enabled for a VPC that has a Classless Inter-Domain Routing (CIDR) that is within the range, with the exce...

Which customer gateway devices can I use to connect to Amazon VPC?

There are two types of VPN connections that you can create: statically-routed VPN connections and dynamically-routed VPN connections. Custo...

What is IPsec?

IPsec is a protocol suite for securing Internet Protocol (IP) communications by authenticating and encrypting each IP packet of a data stre...

How does a hardware VPN connection work with Amazon VPC?

A hardware VPN connection connects your VPC to your datacenter. Amazon supports Internet Protocol security (IPsec) VPN connections. Data tr...

How do instances without public IP addresses access the Internet?

Instances without public IP addresses can access the Internet in one of two ways: Instances without public IP addresses can route their tr...

How do instances in a VPC access the Internet?

You can use public IP addresses, including Elastic IP addresses (EIPs), to give instances in the VPC the ability to both directly communica...

Does Amazon VPC support multicast or broadcast?


What does an Amazon VPC router do?

An Amazon VPC router enables Amazon EC2 instances within subnets to communicate with Amazon EC2 instances in other subnets within the same ...

Does the Amazon VPC VPN Connection have a Service Level Agreement (SLA)?


How many VPCs, subnets, Elastic IP addresses, Internet gateways, customer gateways, virtual private gateways, and VPN connections can you create?

You can have: Five Amazon VPCs per AWS account per region Two hundred subnets per Amazon VPC Five Amazon VPC Elastic IP addresses per ...

Can you use the AWS Management Console to control and manage Amazon VPC?

Yes. You can use the AWS Management Console to manage Amazon VPC objects such as VPCs, subnets, route tables, Internet gateways, and IPSec ...

Can you specify which subnet will use which gateway as its default?

Yes. You may create a default route for each subnet. The default route can direct traffic to egress the VPC via the Internet gateway, the v...

Can you modify the VPC route tables? How?

Yes. You can create route rules to specify which subnets are routed to the Internet gateway, the virtual private gateway, or other instance...

Will ClassicLink settings on my EC2-Classic instance persist through stop/start cycles?

The ClassicLink connection will not persist through stop/start cycles of the EC2-Classic instance. The EC2-Classic instance will need to be...

Does the EC2-Classic instance become a member of the VPC?

The EC2-Classic instance does not become a member of the VPC. It becomes a member of the VPC Security Group that was associated with the in...

How do you use ClassicLink?

In order to use ClassicLink, you first need to enable at least one VPC in your account for ClassicLink. Then you associate a Security Group...

What is ClassicLink?

Amazon Virtual Private Cloud (VPC) ClassicLink allows EC2 instances in the EC2-Classic platform to communicate with instances in a VPC usin...

Is there any bandwidth limitations for peering connections?

Bandwidth between instances in peered VPCs is no different than bandwidth between instances in the same VPC. Note: A placement group can sp...

Is VPC peering traffic within the region encrypted?

No. Traffic between instances in peered VPCs remains private and isolated – similar to how traffic between two instances in the same VPC is...

Do you need an Internet Gateway to use peering connections?

No. VPC peering connections do not require an Internet Gateway.

Can you peer two VPCs with matching IP address ranges?

No. Peered VPCs must have non-overlapping IP ranges.

Can you use AWS Direct Connect or hardware VPN connections to access VPCs I’m peered with?

No. “Edge to Edge routing” isn’t supported in Amazon VPC. Refer to the VPC Peering Guide for additional information.

Can you detach the primary interface (eth0) on my EC2 instance?

No. You can attach and detach secondary interfaces (eth1-ethn) on an EC2 instance, but you can’t detach the eth0 interface.

Can you use Elastic Network Interfaces as a way to host multiple websites requiring separate IP addresses on a single instance?

Yes, however, this is not a use case best suited for multiple interfaces. Instead, assign additional private IP addresses to the instance a...

Can you attach a network interface in one VPC to an instance in another VPC?

Network interfaces can only be attached to instances in the same VPC as the interface.

Can you attach a network interface in one Availability Zone to an instance in another Availability Zone?

Network interfaces can only be attached to instances residing in the same Availability Zone.

Can you have more than two network interfaces attached to my EC2 instance?

The total number of network interfaces that can be attached to an EC2 instance depends on the instance type. See the EC2 User Guide for mor...

Can you peer my VPC with a VPC belonging to another AWS account?

Yes, assuming the owner of the other VPC accepts your peering connection request.

Can you create a peering connection to a VPC in a different region?

No. Peering connections are only available between VPCs in the same region.

What if your peering connection goes down?

AWS uses the existing infrastructure of a VPC to create a VPC peering connection; it is neither a gateway nor a VPN connection, and does no...

Can you attach or detach one or more network interfaces to an EC2 instance while it’s running?


How are IAM accounts impacted by default VPC?

If your AWS account has a default VPC, any IAM accounts associated with your AWS account use the same default VPC as your AWS account.

You really want a default VPC for my existing EC2 account. Is that possible?

Yes, however, we can only enable an existing account for a default VPC if you have no EC2-Classic resources for that account in that region...

You have an existing EC2-Classic account. Can I get a default VPC?

The simplest way to get a default VPC is to create a new account in a region that is enabled for default VPCs, or use an existing account i...

If you peer VPC A to VPC B and I peer VPC B to VPC C, does that mean VPCs A and C are peered?

No. Transitive peering relationships are not supported.

If you delete my side of a peering connection, will the other side still have access to my VPC?

No. Either side of the peering connection can terminate the peering connection at any time. Terminating a peering connection means traffic ...

Can you delete a default subnet?

Yes, but once deleted, it’s gone. Your future instance launches will be placed in your remaining default subnet(s).

Can you delete a default VPC?

Yes. Contact AWS Support if you've deleted your default VPC and want to have it reset.

Do you need to have a VPN connection to use a default VPC?

No. Default VPCs are attached to the Internet and all instances launched in default subnets in the default VPC automatically receive public...

Can you use Amazon EC2 Reserved Instances with Amazon VPC?

Yes. You can reserve an instance in Amazon VPC when you purchase Reserved Instances. When computing your bill, AWS does not distinguish whe...

Can you boot an Amazon EC2 instance from an Amazon EBS volume within Amazon VPC?

Yes, however, an instance launched in a VPC using an Amazon EBS-backed AMI maintains the same IP address when stopped and restarted. This i...

Can you use my existing Amazon EBS snapshots?

Yes, you may use Amazon EBS snapshots if they are located in the same region as your VPC. More details are available in the Amazon EC2 Regi...

What are the differences between instances launched in EC2-Classic and EC2-VPC?

See Differences between EC2-Classic and EC2-VPC in the EC2 User Guide.

Will you need to know anything about Amazon VPC in order to use a default VPC?

No. You can use the AWS Management Console, AWS EC2 CLI, or the Amazon EC2 API to launch and manage EC2 instances and other AWS resources i...

Can you create additional subnets in my default VPC, such as private subnets?

Yes. To launch into nondefault subnets, you can target your launches using the console or the --subnet option from the CLI, API, or SDK.

Can you create other VPCs and use them in addition to my default VPC?

Yes. To launch an instance into nondefault VPCs you must specify a subnet-ID during instance launch.

How can you know if my account is configured to use a default VPC?

The Amazon EC2 console indicates which platforms you can launch instances in for the selected region, and whether you have a default VPC in...

What accounts are enabled for default VPC?

If your AWS account was created after March 18, 2013 your account may be able to launch resources in a default VPC. See this Forum Announce...

What are the advantage of a default VPC?

When you launch resources in a default VPC, you can benefit from the advanced networking functionalities of Amazon VPC (EC2-VPC) with the e...

What is a default VPC?

A default VPC is a logically isolated virtual network in the AWS cloud that is automatically created for your AWS account the first time yo...

Can you launch Amazon EC2 Cluster Instances in a VPC?

Yes. Cluster instances are supported in Amazon VPC, however, not all instance types are available in all regions and Availability Zones.

How many default subnets are in a default VPC?

One default subnet is created for each Availability Zone in your default VPC.

What is the IP range of a default VPC?

The default VPC CIDR is Default subnets use /20 CIDRs within the default VPC CIDR.

How many default VPCs can you have?

You can have one default VPC in each AWS region where your Supported Platforms attribute is set to "EC2-VPC".

Can you employ Auto Scaling within Amazon VPC?


How many Amazon EC2 instances can you use within a VPC?

You can run any number of Amazon EC2 instances within a VPC, so long as your VPC is appropriately sized to have an IP address assigned to e...

When you call DescribeVolumes(), do you see all of my Amazon EBS volumes, including those in EC2-Classic and EC2-VPC?

Yes. DescribeVolumes() will return all your EBS volumes.

When you call DescribeInstances(), do you see all of my Amazon EC2 instances, including those in EC2-Classic and EC2-VPC?

Yes. DescribeInstances() will return all running Amazon EC2 instances. You can differentiate EC2-Classic instances from EC2-VPC instances b...

How do you determine which Availability Zone my subnets are located in?

When you create a subnet you must specify the Availability Zone in which to place the subnet. When using the VPC Wizard, you can select the...

What are the differences between security groups in a VPC and network ACLs in a VPC?

Security groups in a VPC specify which traffic is allowed to or from an Amazon EC2 instance. Network ACLs operate at the subnet level and e...

How do you secure Amazon EC2 instances running within my VPC?

Amazon EC2 security groups can be used to help secure instances within an Amazon VPC. Security groups in a VPC enable you to specify both i...

Are there any bandwidth limitations for Internet gateways? Do you need to be concerned about its availability? Can it be a single point of failure?

No. An Internet gateway is horizontally-scaled, redundant, and highly available. It imposes no bandwidth constraints.

How do you specify which Availability Zone my Amazon EC2 instances are launched in?

When you launch an Amazon EC2 instance you must specify the subnet in which to launch the instance. The instance will be launched in the Av...

Can you employ Amazon CloudWatch within Amazon VPC?


Can you use your existing AMIs in Amazon VPC?

You can use AMIs in Amazon VPC that are registered within the same region as your VPC. For example, you can use AMIs registered in us-east-...

Can a VPC span multiple Availability Zones?


Within which Amazon EC2 region(s) is Amazon VPC available?

Amazon VPC is currently available in multiple Availability Zones in all Amazon EC2 regions. 

Can you monitor the network traffic in your VPC?

Yes. You can use the Amazon VPC Flow Logs feature to monitor the network traffic in your VPC. Amazon VPC & EC2

Why can’t you ping the router, or my default gateway, that connects my subnets?

Ping (ICMP Echo Request and Echo Reply) requests to the router in your VPC is not supported. Ping between Amazon EC2 instances within VPC i...

Can Amazon EC2 instances within a VPC communicate with Amazon EC2 instances not within a VPC?

Yes. If an Internet gateway has been configured, Amazon VPC traffic bound for Amazon EC2 instances not within a VPC traverses the Internet ...

Within Amazon VPC, can you use SSH key pairs created for instances within Amazon EC2, and vice versa?


What is the difference between stateful and stateless filtering?

Stateful filtering tracks the origin of a request and can automatically allow the reply to the request to be returned to the originating co...

Why should you use Amazon VPC, Advantage of using AWS VPC?

Amazon VPC enables you to build a virtual network in the AWS cloud - no VPNs, hardware, or physical datacenters required. You can define yo...

What are the components of Amazon VPC?

Amazon VPC comprises a variety of objects that will be familiar to customers with existing networks: A Virtual Private Cloud (VPC): A l...

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