AWS

Architecture

5 Pillars

Security, Reliability, Performance Efficiency, Cost Optimization, Operation Excellence.

Web Tier: It contains web servers like Apache. App Tier: It contains app servers. Database Tier: It contains database services like Amazon RDS (Relational Database Service).

When a user visits the app URL, it gets checked by the DNS (Domain Name System) management system called Route 53.

The user request will then go through the load balancer that maintains all the incoming and outgoing traffic.

This traffic will finally go to the web and app tier and then connect with the database tier.

The database tier contains one Amazon ElastiCache for fast data access and one Amazon RDS DB Instance. One more Amazon RDS DB Instance is present in Availability Zone 2 that will act as a standby database for disaster recovery solutions.

One S3 Bucket connects with the Web tier and the database tier for the backup solution to store the static data like images and GIFs.

The request to access the content will go to the Content Delivery Network that is CloudFront.

Also, this complete Architecture can integrate with other services like CloudWatch, Amazon Dynamo DB, SES, AWS SNS, and more.

VPC

VPC is a virtual network inside AWS for one client

AWS supported CIDR block range

The allowed block size is between a /16 netmask (65,536 IP addresses) and /28 netmask (16 IP addresses).

Resource	Default limit
VPCs per Region	5
Subnets per VPC	200
IPv4 CIDR blocks per VPC	5
IPv6 CIDR blocks per VPC	5

Public IP:

Public IP means the machine can be identified on the internet (WWW)

Must be unique across the whole web (not two machines can have the same public IP).

Can be geo-located easily

Private IP:

Private IP means the machine can only be identified on a private network only

The IP must be unique across the private network

BUT two different private networks (two companies) can have the same IPs.

Machines connect to WWW using an internet gateway (a proxy)

Only a specified range of IPs can be used as private IP

Note: When you stop/start your instance, the IP address will change. If you reboot the instance, it will keep the same IP addresses. Unfortunately, it is not possible for us to reassign the address to your instance as that address would have been released back into the pool used by other EC2 instances.

Security Groups

Can be attached to multible instances. • Locked down to a region / VPC combination. • Does live "outside" the EC2 - if traffic is blocked the EC2 instance won't see it. • If your application is not accessible (time out), then it's a security group issue. • If your application gives a "connection refused" error, then it's an application error or it's not launched. • All inbound traffic is blocked by default

ALB vs NLB vs CLB

Feature	Application Load Balancer	Network Load Balancer	Classic Load Balancer
Layer	Layer 7	Layer 4	Layer 4
Protocols	HTTP, HTTPS	TCP, TLS	TCP, SSL/TLS, HTTP, HTTPS
Platforms	VPC	VPC	EC2-Classic, VPC
Health checks	✔	✔	✔
CloudWatch metrics	✔	✔	✔
Logging	✔	✔	✔
Zonal fail-over	✔	✔	✔

Application Load Balancer

Web applications with L7 routing (HTTP/HTTPS)

Microservices architectures (e.g. Docker containers)

Lambda targets

Network Load Balancer

TCP and UDP based applications

Ultra-low latency

Static IP addresses

Gateway Load Balancer

Load balance virtual appliances such as:

Intrusion detection systems (IDS)

Intrusion prevention systems (IPS)

Next generation firewalls (NGFW)

Web application firewalls (WAF)

Distributed denial of service protection systems (DDoS)

Versioning Objects in S3

Cannot Be Disabled: Once enabled, versioning cannot be disabled; it can only be suspended temporarily if needed.

All Versions: All versions of an object are stored in S3, including all writes and even if an object is deleted.

Lifecycle Rules: Versioning can be integrated with lifecycle rules, allowing you to automate the transition of object versions between different storage tiers.

Supports MFA: Versioning supports multi-factor authentication, adding an extra layer of security to protect your data.

S3 Lifecycle Management

Automates moving objects between different storage tiers.

Can be used in conjunction with versioning.

Can be applied to current versions and previous versions.

Auto Scaling

Dynamic Scaling Policies

Target Tracking Scaling

Most simple and easy to set up

Example: We want the average ASG CPU to stay at around 40%

Simple/Stepped Scaling

When a CloudWatch Alarm is triggered (ex: CPU > 70%), then add 2 units

When CloudWatch alarm is triggered (ex: CPU < 30%), then remove 1

Scheduled Actions

Anticipate a scaling based on known usage patterns

Ex: increase the min capacity to 10 at 5pm on Fridays

RDS

ㅤ	RDS Multi-AZ	Read Replicas
Description	An exact copy of your production database in another Availability Zone.	A read-only copy of your primary database in the same AZ, cross-AZ, or cross-region.
Purpose	Used for DR (Disaster Recovery).	Used to increase or scale read performance.
Failover	In the event of a failure, RDS will automatically failover to the standby instance.	-
Workload Type	-	Great for read-heavy workloads and takes the load off your primary database for read-only workloads.
Example Use Case	-	Business Intelligence reporting jobs.

RDS Automated Backup

Point-In-Time Recovery: Recover your database to any point in time within a "retention period" of 1-35 days.

Full Daily Backup: RDS takes a full daily backup, or snapshot, and also stores transaction logs throughout the day.

The Recovery Process: When you perform a recovery, AWS will first choose the most recent daily backup. AWS then applies transaction logs relevant to that day, up to the recovery point.

RDS Snapshots:

Snapshots are not automated: DB Snapshots are performed manually, meaning they are initiated by the user.

No Retention Period: Manual snapshots are not deleted, even if the original RDS instance, along with any automated backups, is deleted.

Backup to a Known State: You have the ability to back up your DB instance to a known state as frequently as desired. This allows you to restore to a specific state at any given time.

Migration of Database from EC2 to RDS Database


# ec2db is the current db 
# rdsdb is the RDS db which is created when RDS is configured.
# -p = password
# -P = port
mysqldump -u root -p ec2db > ec2db.sql
mysql -h <replace-rds-end-point-here> -P 3306 -u rdsuser -p rdsdb < ec2db.sql
mysql -h <replace-rds-end-point-here> -P 3306 -u rdsuser -p

# Commands to check the db if migrated properly 
USE rdsdb
SELECT * FROM table1;

SQl vs NoSQL

Feature	SQL	NoSQL	Best Use Case
Data Structure	Structured	Unstructured	Well-defined, structured data with complex relationships
Query Language	SQL	Varies by database	Complex queries, joins, transactions, and reporting
Scalability	Vertical	Horizontal	Traditional scaling with vertical hardware resources
Schema	Fixed	Dynamic	Rigid, predefined schema, and data consistency requirements
Flexibility	Limited	High	Agile development, frequent schema changes, evolving needs
Performance	Optimized for complex queries and joins	Varies by database	High-speed data retrieval, real-time data analysis and high-throughput scenarios
Examples	MySQL, Oracle, Redshift, PostgreSQL, Oracle, SQL Server, and AWS Aurora	MongoDB, Redis, DynamoDB	E-commerce platforms, financial systems, content management systems, real-time analytics

Route53

Route 53 is AWS's Domain Name System (DNS) service. It serves as the DNS resolver for VPCs and typically operates on the IP address 169.254.169.253 within a VPC.

Route 53 performs three main functions:

Domain registration

DNS routing

Health checking.

Zones are utilized with DNS servers to store records related to a domain. Examples of top-level domains include amazon.com, example.com, and swas.in. Sub-domains, such as academy.amazon.com, are also common. Zones hold DNS record set information, including details about the authoritative name server for a particular domain name. Route 53 provides hosted zones, which act as containers for DNS records. Each zone includes information about the IP address to which a domain name resolves and the mail server to which email should be forwarded.

AWS offers two types of hosted zones:

Public hosted zones, which hold records specifying how to route internet-based traffic.

Private hosted zones, which hold records specifying how to route traffic within a VPC.

Other Services