Cloud Concepts Dive Deep

AWS Disaster Recover Strategies

Disaster recovery refers to how we restore the services & data when the system fails of services goes down

Active/Passive Strategies

•    Backup-Restore (RPO & RTO in hours)
•    Pilot-Light  (Services Idle / RPO & RTO in 10s of minutes)
•    Warm-Standby (Always running / RTO & RPO in minutes)

Active/Active

•  Multi-Region  (RPO & RTO in real time)

RPO - Recovery Point Objective is mainly concerned about the Data Loss

RTO - Recovery Point Objective is mainly concerned about the Down Time 

Difference between NACL & Security Groups

NACLs	SGs
NACLs works as firewalls for SubNets	SGs acts as Firewalls for EC2 instances
NACLs are State Less	SGs are State Full
Change applied to an incoming rule isn't automatically applied to an outgoing rule	Any changes applied to an incoming rule will be automatically applied to the outgoing rule
NACL rule can either allow or deny traffic	SGs rules are always permissive; We can't create SG rule that deny access
By default, NACLs allow all inbound and outbound traffic	By default, SGs allow all outbound traffic

Authentication vs Authorization

• Authentication is the process of verifying who someone is (Providing access credentials). Authentication validates a user's identity.

• Authorization is the process of verifying what specific applications, files, and data a user has access to (Assigning the roles and groups). Authorization grants that user permission to access a resource

Symmetric Encryption & Asymmetric Encryption

• Symmetric encryption uses one key for both encryption and decryption. Example for Symmetric encryption are AES, DES

• Asymmetric encryption uses two separate keys, one for encryption and another for decryption. Example for Asymmetric encryption is SFTP, SSH, SCP which uses RSA or DSA keys as public and private keys

Note : 

• AWS KMS supports both symmetric and asymmetric encryption
• SSL/TLS uses both asymmetric and symmetric encryption

Cloud Computing

Cloud computing is the on-demand delivery of IT resources over the Internet with pay-as-you-go pricing.

Serverless Computing

A serverless architecture is a way to build and run applications and services without having to manage infrastructure.

NAT - Network Address Translation 

• It's a way to map multiple local private addresses to a public one before transferring the information.
• NAT device used to allow instances in private subnets to connect to the internet

CI/CD - Continuous Integration and Continuous Delivery 

• Continuous integration is a DevOps software development practice where developers regularly merge their code changes into a central repository

• Continuous delivery is where code changes are automatically built, tested, and prepared for a release to production

AWS Provides various tools to strategize the CI/CD pipeline

• CodePipeline - Like an uDeploy
• CodeCommit - Like an SVN,GitHub
• CodeBuild - Like a Jenkin
• CodeDeploy-ElasticBeanStack
• CodeStar - It is for testing the project resources, et a holistic view of your projects.
• CodeArtifect - It is for storing and retrieving the code/package dependencies
• CodeGuru - Machine Learning powered service for automated code reviews and application performance recommendation.

CAPEX	OPEX
Capital Expenditures	Operating Expenses
(CAPEX) is an expenses incurred in order to create long-term benefits in the future	(OPEX) is an expense required for the day-to-day functioning of a business

Difference Between Views and Materialized Views

View	Materialized View
Views are not stored physically on the disk	Materialized views are stored physically on the disk
View is a virtual table created as result of the query	Materialized views are snapshot of the base table
A view is updated automatically when the query creating that view executes	But the Materialized view is updated manually or by applying triggers to it
Views are not precomputed	Materialized views are precomputed
Views responds slower than the Materialized View	Materialized View responds faster

ACID - Atomicity, Consistency, Isolation, Durability

CDN - Content Delivery Network

• Content delivery networks provide a globally-distributed network of proxy servers that cache content, such as web videos or other bulk media.

• CDN reduces the load on application origin and improves user experience

Difference between Relational Databases & NoSQL Databases

Relational Databases (RDBMS)	NoSQL Databases
RDMS stores data in Rows and Column format	NoSQL stores the data in Key Value and Document format
Oracle, MySQL, PostgreSQL	DynamoDB, MongoDB, MariaDB
Relational Databases are used for OTLP, OLAP applications	NoSQL databases are used for low-latency applications like Social Media, Gaming applications
Relational databases provides Schema and Table like structure	NoSQL Doesn't support  Schema and Table like structure
Relational DBs can be queried using the SQL statements	NoSQL DBs can be queried using the APIs

     

Types of NoSQL Databases

• Key-value
• Document
• In-memory
• Search

What is IOPs

• Input/output operations per second
• Which measures how fast data can be transferred from contiguous storage locations
• IOPS can be used to measure storage performance

Throughput 

Throughput refers to how much data can be transferred from one location to another in a given amount of time

Latency

Latency is how long does it takes for a data to travel between its source and destination, total round trip time. 

Fault-tolerance 

• Is the ability for a system to remain in operation even if some of the components used to build the system fail
• Is the ability of a system to withstand the failure

Horizontal Vs Vertical Scaling

• Horizontal scaling means that you scale by adding more ec2 machines into your pool of resources
• Vertical scaling means that you scale by adding more power (CPU, RAM) to an existing ec2 machine

Tools used to gauge the network throughput/issues
 
    tracert or traceroute
    AWS CloudWatch
    Elastic Network Adapter (ENA) 
    NewRelic & DataDog
    AppDynamics

CIDR - Class Less Inter Domain Routing

    CIDR used for specifying a range to IP addresses in format of IPv4 or IPv6

WAF - Web Application Firewall

•  Used to protect the web applications from threats like SQL Injections, Web Exploits &  Bots  that may  affect availability and security.
•  WAF helps to black listing and Whitelisting the IPs addresses
•  WAF works well with CloudFront, API Gateway and ALB

DOS - Denial of Service

DDoS - Distributed Denial of Service

Difference between the Containers and Server less

 Containers are hosted in the cloud, but cloud providers do not update or maintain them. Customer/Vendors have to manage and update each containers they deployed.

Containers take longer to set up initially than server less functions because it is necessary to configure system settings, libraries, and so on

Once configured, containers take only a few seconds to deploy

Containers give developers more control over the environment the application runs in.

Containers run the same no matter where they are deployed, making it relatively simple to test 

Containers are constantly running, and therefore cloud providers have to charge for the server space even if no one is using the application at the time

Persistent storage issue with the containers: data doesn't persist when that container go down

 In server less architecture customers are being charged only when the application code is being executed (Lambda)

Server less takes milliseconds to deploy since those do not come up with system dependencies

It is difficult to test server less web applications because the backend environment is hard to replicate on a local environment

Elastic IP

• When we start and stop an EC2 instance, the public IP of the machine will change
• If we want to have a fixed public IP we need an Elastic IP
• An Elastic IP is a Public IPv4
• We don’t pay for the Elastic IP if it’s assigned to the server & we pay only when it is not assigned
• Default limit for an account is 5 Elastic IPs

Address Resolution Protocol (ARP) is a protocol or procedure that connects an ever-changing Internet Protocol (IP) address to a fixed physical machine address, also known as a media access control (MAC) address

LAMP Stack 

• Is a set of open-source software that can be used to create websites and web     applications
•  Linux, Apache, MySQL, PHP

Synchronous and Asynchronous Calls

Linux command used for searching

grep 
find
locate
whereis

Difference between TCP and UDP

TCP	UDP
TCP is a connection-oriented protocol	UDP is a connectionless protocol
TCP is slower	UDP is faster
TCP uses handshake protocol	UDP uses no handshake protocols
For Ex : SFTP, SSL, SCP	For Ex : VPN, VOIP, Online Games & Media Streaming

Difference between TCP and HTTP

TCP	HTTP
Transmission Control Protocol	Hyper Test Transfer Protocol
TCP is connection oriented protocol	HTTP is connection less protocol
Layer 4	Layer 7
TCP is slower	HTTP is faster
TCP operates 3-way communication	HTTP operates single-way communication

 

OSI Reference Model (Open System Interconnection)

7	Application Layer	HTTP, SFTP, FTP, SSH, DNS
6	Presentation Layer	SSL
5	Session Layer	API's, Sockets
4	Transport Layer	TCP, UDP
3	Network Layer	IP, IPSec, ICMP
2	DataLink Layer	Ethernet, Bridge, Switch
1	Physical Layer	Fiber, Coax, Wireless

Difference between Normalization and Denormalization of data

    

Normalization	DeNormalization
Process of organizing data in a database by reducing the redundancy	Is a technique in which we add the duplicate data to one or more table
Maintain Data Integrity	Doesn't Maintain Data Integrity
For Ex : OLTP Databases	For Ex: OLAP / Data Warehouse Databases
Used when high intensive INSERT/UPDATE/DELETE operations are performed	Used when expensive joins are required & frequent read queries are executed
Number of tables are less	Number of tables are more
Normalization uses optimized memory and hence faster in performance	Denormalization introduces some sort of wastage of memory

Hypervisor

• Hypervisor is a software program helps to run multiple virtual machines on a single computer hardware

• The new hypervisor for AWS EC2 is a component that delivers memory isolation and CPU for all the C5 instances

JSON Vs XML

      

JSON	XML
JavaScript Object Notation	Extensible markup language
It is a way of representing objects	It is a way of representing Data Items using tags
It does not provides any support for namespaces	It supports namespaces
It supports array	It doesn’t supports array
It supports only UTF-8 encoding	It supports various encoding

Monolithic Vs Microservices

     

Monolithic	Microservices
A monolithic application is built as a single and indivisible unit	Microservices architecture breaks the software architecture  into a collection of smaller independent units
Tightly-Coupled	Loosely-Coupled
Traditional Approach	Modern Approach
Hard to scale	Easy to scale

      

Discuss durability vs availability

3 Tier architecture with a static content

A three-tier architecture is a software architecture pattern where the application is broken down into three logical tiers: The Presentation Layer, Application Layer (Logic Tier) and the Data Storage Layer

This architecture is used in a client-server application such as a web application that has the frontend, the backend and the database.

As far as the static content is concerned we can host the static content on the S3 and can use the CloudFront to distribute the content and cache the data at edge location for low latency

We can host the database on the private subnet for better security and application on the public subnet

Difference between WAF and Firewall

Steps involved from entering a web address on browser to you get access

Difference between horizontal and vertical scaling?

What's Monolithic vs Microservices? Use cases for each?

Difference between Database vs. Data Warehouse?

Tell me What is a hypervisor?

Layer 4 and Layer 7 load balancer and how they work?

how would you horizontally and/or vertically scale a multi-tier architecture?

Clustered database environment. and how do you expand and enlarge if need be?

Difference between a cluster and mirroring?

What is RAID 1 and 5

What is an index used for?

How would the migration of a company's infrastructure be carried out with the shortest possible downtime?

explain how secure TLS communication works?

what is DevSecOps? what is the difference between DevOps and DevSecOps

What is DNS? Could you please explain the whole process of how DNS works?

Could you please explain how SSL handshake happens step by step?

What is the difference between a Docker container and a Docker image?

What is Copy on Write in Docker?

How is NoSQL is more scalable than the SQL databases?

describe blue/green deployment?

What is CAP theorem?

what are application development methodology did you use?

How does the internet work?

Partitioning data. why important

AVRO vs ORC vs Parquet

what is RAID. what is RAID-10. what are 2 other types of RAID.

how would you horizontally scale a multi-tier architecture at the top level (network)?

what is RAID. what is RAID-10. what are 2 other types of RAID.

what is layer 3 of the OSI model. Describe

Load Balancer? What is HTTP Socket? What is reverse proxy ? Components of HTTP call?

What is fan and nest storage ?

Difference between encryption and hashing ?

What is indexing ? Give the example of bad index. Why is it a bad index ? How does indexing work ? A connection to database is made using an app, but it's not returning a response. How do you debug this ?

What is HTTP Socket? What is reverse proxy ? Components of HTTP call?

What's Datalake vs Data Warehouse?

What's Monolithic vs Microservices?

What's level 7 load balancer?

Map reduce Broadcast , multicast, unicast?

App service vs web service

SCSI disk?

what is layer 2 and 3 on OSI model

IDS, IPS

What are the levels of RAID

MPLS, HDFS, OSI Model, DataWarehouse, MicroServices, Sharding,

why you should use a CDN for a object with a zero TTL?

What is the difference between an IPSec and an SSL VPN

Discuss SSD vs traditional disk

What is a Bastion host?

Where are customer encryption keys stored

How would you mitigate a DOS?

What are the RAID levels

What are the benefits of ci/cd

What else would you do for a high volume distributed app web site

What is database indexing and why is it important

Troubleshoot a webpage that can't access the DB Troubleshoot why you can't access a webpage server

What is MSA

If you collected logs and wanted to store them for 14 days then move them over to permanent storage for a few years how would you do this How would you analyze objects stored in S3 and share them with users

What ports do databases use 

 Describe how you would build a content delivery network from scratch by coding it

What are the steps involved in migrating customer application from Azure cloud to AWS.

What is "MQTT"?

How do you stop apache service

What is Virtualization? What is a Hypervisor and how does it work to distinguish multiple VMs running on it and isolate them from the underlying h/w?