Day-7 AWS-CSA

1] What is Scalability in AWS

Scalability in Amazon Web Services (AWS) refers to the ability of cloud resources to automatically adjust based on workload demands, ensuring high availability and cost efficiency. AWS provides both vertical and horizontal scalability to meet different application needs.

Types of Scalability in AWS

1. Vertical Scalability (Scaling Up)

• Increasing the capacity of a single AWS resource (e.g., adding more CPU, RAM, or storage to an EC2 instance).
• Example: Upgrading an EC2 instance from t2.micro to t2.large to handle more traffic.
• AWS Services:Amazon EC2 (Resizable virtual machines)Amazon RDS (Database instances can be upgraded)

2. Horizontal Scalability (Scaling Out)

• Adding multiple instances/resources to distribute the workload across multiple machines.
• Example: Adding multiple EC2 instances behind an Elastic Load Balancer (ELB) to handle high traffic.
• AWS Services:Auto Scaling (Automatically adds/removes EC2 instances based on demand)Elastic Load Balancer (ELB) (Distributes traffic among multiple servers)Amazon EFS (Scalable storage system that expands automatically)Amazon S3 (Highly scalable object storage)Amazon DynamoDB (Scales automatically based on request load)

Examples of Scalability in AWS

• Web Applications: A website hosted on EC2 with an Auto Scaling Group (ASG) to add instances during high traffic periods.
• Databases: Amazon RDS allows read replicas for distributing database queries across multiple servers.
• File Storage: Amazon EFS automatically scales storage capacity as files are added or removed.

2] What is High Availability in AWS ?

High Availability (HA) in AWS refers to designing systems that remain operational with minimal downtime, even during failures. AWS achieves HA by distributing resources across multiple data centers and automatically handling failures.

Key Aspects of High Availability in AWS

1. Fault Tolerance – The system continues to function despite failures (e.g., hardware, network, or software issues).
2. Redundancy – Multiple instances of critical components prevent single points of failure.
3. Automatic Failover – AWS services can automatically switch to backup resources when failures occur.
4. Load Balancing – Distributes traffic across multiple instances to prevent overload.

AWS Services for High Availability

• Amazon EC2 Auto Scaling – Automatically replaces failed instances and adds/removes resources based on demand.
• Elastic Load Balancing (ELB) – Distributes incoming traffic across multiple servers to prevent downtime.
• Amazon Route 53 – Provides DNS failover to switch traffic to healthy resources.
• Amazon RDS Multi-AZ – Automatically replicates databases across multiple availability zones for failover support.
• Amazon EFS & S3 – Provide durable, highly available storage solutions.

Example of High Availability in AWS

• A web application is hosted on multiple EC2 instances across different Availability Zones (AZs) behind an ELB.
• Auto Scaling ensures new instances are launched if any fail.
• Route 53 redirects traffic to healthy instances in case of failures.
• RDS Multi-AZ ensures the database remains accessible even if the primary instance fails.

3] What is Load balancing in AWS ?

Load Balancing in AWS is the process of distributing incoming network traffic across multiple resources (such as EC2 instances, containers, or IP addresses) to ensure better performance, high availability, and fault tolerance. AWS provides a fully managed service called Elastic Load Balancer (ELB) to handle load balancing automatically.

Types of Load Balancers in AWS

AWS offers different types of Elastic Load Balancers to suit various use cases:

1. Application Load Balancer (ALB)
2. Network Load Balancer (NLB)
3. Gateway Load Balancer (GWLB)
4. Classic Load Balancer (CLB) [Legacy]

Benefits of Load Balancing in AWS

? High Availability – Distributes traffic across multiple instances to prevent failures.

? Scalability – Works with Auto Scaling to handle traffic spikes dynamically.

? Security – Integrates with AWS WAF and supports SSL termination for secure connections.

? Performance Optimization – Ensures even distribution of workloads, preventing bottlenecks.

Example of Load Balancing in AWS

Imagine a web application running on multiple EC2 instances across multiple Availability Zones (AZs):

1?? Users send requests → Requests hit an Application Load Balancer (ALB)

2?? ALB routes traffic → Based on URL path, it forwards requests to appropriate EC2 instances

3?? Auto Scaling → Automatically adds or removes instances based on traffic demand

4?? Health Checks → If an EC2 instance becomes unhealthy, ALB routes traffic to healthy instances

4] Why use a load balancer ?

A load balancer is essential for modern applications to ensure they are fast, reliable, and scalable. Here’s why you should use a load balancer:

1. High Availability

• Distributes traffic across multiple servers, ensuring that if one server fails, others continue to handle requests.
• Prevents single points of failure, enhancing system uptime.

2. Scalability

• Works with auto-scaling to dynamically add or remove servers based on demand.
• Handles traffic spikes without manual intervention, ensuring consistent performance.

3. Improved Performance

• Balances the workload evenly among servers, preventing any single server from becoming a bottleneck.
• Reduces response time by routing requests to the most available or least busy server.

4. Fault Tolerance

• Monitors the health of servers and automatically reroutes traffic if a server becomes unresponsive.
• Ensures continuous service even during server maintenance or failures.

5. Security

• Integrates with firewalls and supports SSL termination to manage secure connections efficiently.
• Helps protect against DDoS attacks by distributing incoming traffic.

6. Flexible Routing

• Supports path-based and host-based routing (e.g., different URLs can be routed to different servers or services).
• Enables blue/green deployments and A/B testing by directing traffic to different environments.

7. Simplified Management

• Provides a single point of entry for all incoming traffic, making it easier to manage complex architectures.
• Reduces the complexity of DNS configurations by abstracting server details.

Real-World Example:

For an e-commerce website, a load balancer ensures:

• Smooth handling of high traffic during sales.
• No downtime if a server crashes.
• Faster load times by routing users to the nearest or fastest server.

5] Application Load balancer

What is an Application Load Balancer (ALB)?

An Application Load Balancer (ALB) is a Layer 7 (HTTP/HTTPS) load balancer that routes traffic based on content, hostnames, paths, and query parameters. It’s designed for modern web applications, microservices, and API-based architectures.

?? Key Features:

? Intelligent routing (Path-based, Host-based)

? WebSockets & HTTP/2 support

? Sticky Sessions & SSL termination

? Integrated security with AWS WAF ? Auto Scaling & High Availability

Why Use an Application Load Balancer?

?? 1. Intelligent Request Routing (Content-Based Routing)

ALB allows you to route traffic based on:

?? Path-based routing: /login → Auth service, /orders → Orders service ?? Host-based routing: api.example.com → API service, app.example.com → Frontend service

? Example: A microservices-based app routes:

• /api/users → User Service
• /api/orders → Order Service

?? 2. Load Balancing Across Multiple Targets

ALB can distribute traffic across multiple target types:

• EC2 instances
• Containers (ECS, EKS)
• Lambda functions
• IP addresses

? Example: A multi-region e-commerce app routes users to the nearest AWS region for better performance.

?? 3. Auto Scaling & High Availability

ALB works with Auto Scaling to add or remove instances automatically, ensuring the app handles sudden traffic spikes smoothly.

? Example: During Black Friday sales, new EC2 instances launch as traffic increases, and ALB distributes requests evenly.

?? 4. Enhanced Security & SSL Termination

ALB supports SSL/TLS termination, which secures incoming traffic before forwarding it to backend servers. It also integrates with AWS Web Application Firewall (WAF) to block malicious requests.

? Example: A banking website uses HTTPS with ALB to protect sensitive transactions.

?? 5. Sticky Sessions (Session Persistence)

ALB supports sticky sessions (session affinity), ensuring a user’s requests are always directed to the same server.

? Example: An online shopping cart stays consistent by directing all requests from the same user to a specific EC2 instance.

?? 6. WebSocket & HTTP/2 Support

ALB supports WebSockets for real-time applications and HTTP/2 for faster performance.

? Example: A live chat application uses WebSockets via ALB for real-time messaging.

How Does an Application Load Balancer Work?

1?? Client Request → ALB receives a request.

2?? Routing Decision → ALB checks the request (host, path, query params, headers).

3?? Target Group Selection → ALB forwards the request to the right target group (EC2, ECS, Lambda).

4?? Health Check → ALB ensures only healthy targets receive traffic.

5?? Response to Client → The backend processes the request and sends a response.

Use Case Scenarios for ALB

? Microservices Architecture – Routes different paths to different services (/api/users, /api/orders).

? Secure Web Applications – Uses HTTPS, WAF, and sticky sessions for user sessions.

? Serverless Apps – Routes traffic to AWS Lambda without needing EC2 instances.

? Containerized Apps (ECS, EKS) – Balances load across Docker containers.

6] What is Application load balancer target Groups

A Target Group is a collection of backend resources (EC2 instances, Lambda functions, IP addresses, or containers) that receive traffic from an Application Load Balancer (ALB).

Each Target Group has health checks, which monitor the availability of the backend targets and route traffic only to healthy targets.