High Availability and Scalability: ELB & ASG

Question 1

Horizontal Scalability

Answer 1

Increasing the number of instances, systems for your application. Horizontal scaling implies distributed systems.

Question 2

Vertical Scalability

Answer 2

Increasing the size of the instance. common for non distributed systems such as database. RDS and Elasticache are services that can scale vertically.

Question 3

High Availability

Answer 3

running application, system in at least 2 data centers. the goal of high availability is to survive data center loss.

Question 4

Load Balancing

Answer 4

Load Balancers are Servers that forward traffic to multiple servers downstream.

Question 5

Why use Load Balancers?

Answer 5

• Spread load across multiple downstream instances
• Expose a single point of access (DNS) to your application * Seamlessly handle failures of downstream instances
• Do regular health checks to your instances
• Provide SSL termination (HTTPS) for your websites
• Enforce stickiness with cookies
• High availability across zones
• Separate public traffic from private traffic

Question 6

Types of Load Balancers?

Answer 6

Classic Load Balancer (v1 - old generation) – 2009 – CLB * HTTP, HTTPS,TCP,SSL(secureTCP)
* Application Load Balancer (v2 - new generation) – 2016 – ALB * HTTP, HTTPS,WebSocket
* Network Load Balancer (v2 - new generation) – 2017 – NLB * TCP,TLS(secureTCP),UDP
* Gateway Load Balancer – 2020 – GWLB
* Operates at layer 3 (Network layer) – IP Protocol

Question 7

Application Load Balancer

Answer 7

• Application load balancers is Layer 7 (HTTP)
• Load balancing to multiple HTTP applications across machines (target groups)
• Load balancing to multiple applications on the same machine (ex: containers)
• Suppor t for HTTP/2 and WebSocket
• Support redirects (from HTTP to HTTPS for example)