ELB

Question 1

What is vertical scalability?

Answer 1

scaling from something smaller (i.e t2mcro) to something larger (i.e t2large)

Question 2

What is horizontal scalibility?

Answer 2

Implies distributed systems

Increase the # of instances running (i.e add an EC2 instance lke a t2micro rather then scaling vertically to a larger instance)

AKA scaling up or scaling down

Question 3

What is high availability?

Answer 3

usually goes hand in hand with horizontal scaling (but not always)

Also refered to as scaling out or scaling in

Means running the application in at LEAST 2 Availability Zones

Goal is to survive a AZ zone loss

Question 4

What is load balancing?

Answer 4

Load balancers are servers that forward internet traffic to multiple servers (EC2 Instances) downstream.

Question 5

Why use load balancer (8)?

Answer 5

Spread load across multiple downstream instances.
Expose 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) to your websites.
Enforces stickiness with cookies
High availability across zones
Separates public traffic from private traffic.

Question 6

What are the three types of load balancers offered by AWS?

Answer 6

Classic (legacy)
Application
Network

Question 7

What type of traffic does the Classic load balancer support?

Answer 7

HTTP & HTTPS (Layer 7),

TCP (Layer 4)

Question 8

What type of traffic does the Application Load Balancer support?

Answer 8

HTTP & HTTPS (Layer 7),

WebSocket

Question 9

What type of traffic does the Network Load Balancer Support?

Answer 9

TCP,
TLS (secure TCP),
UDP

Question 10

T/F Load balancers can be both public or private

Answer 10

True

Question 11

What is load balancer stickiness?

Answer 11

The same clients gets redirected to the same EC2 instance every time. Helps ensure session data isn’t lost.

Works for classic and application LB.

The cookie used for stickiness has an expiration date you control.

Question 12

(T/F) Cross zone load balancing is not enabled by default for ANY load balancers.

Answer 12

FALSE.

Cross zone zone load balancing IS ALWAYS ON for application load balancers, and there in NO charge for this service.

It is disabled by default on both Classic and Network LBs.

There is no charge on CLB if enabled.

There IS a charge on NLB if enabled.

Question 13

What is Server Name Indication (SNI) & how to ELBs play a role?

Answer 13

SNI solves the problem of loading multiple SSL certs onto one web server to serve MULTIPLE websites.

Its a newer protocol and requires the client to indicate the hostname of the target server in the initial SSL handshake

Only works on ALB and NLB

Question 14

T/F Classic load balancers can only support one SSL certificate

Answer 14

TRUE

Question 15

What is Connection Draining

Answer 15

Connection Draining, AKA Deregistration Delay (ALB & NLB) is when an EC2 instance begins the shutdown process because it was determined to be unhealthy. During this draining process, existing connections are first being completed before complete shutdown.

New requests are NOT sent to the instance while in this stage.

Question 16

What are the 4 main goals of an auto scaling group (ASG)?

Answer 16

Scale out to match increased load (add instances)

Scale in to match decreased load (remove instances)

Ensure we have min and max number of instances running

Automatically register new instances to a load balancer

Question 17

What are Scaling policies based on?

Answer 17

AS Policies can be based on any # of factors such as CPU useage, network, and schedule or even custom metrics

Question 18

What AWS Services are used to launch ASGs?

Answer 18

Launch configurations or Launch templates (newer)

Question 19

What is the cost of ASGs?

Answer 19

ASGs are free. You pay for the underlying services (i.e. EC2 instances)

Question 20

What are the 3 main ASG Scaling Policies?

Answer 20

Target Tracking Scaling
Simple/Step Scaling
Schedules Actions

Question 21

What is Target Tracking Scaling?

Answer 21

Most simple Scaling policy to set up.

Example -I want average ASG CPU to stay around 40%

Question 22

What is Simple/Step Scaling?

Answer 22

Scale in and Scale out policies can be defined using CloudWatch.

Example set CloudWatch alarm to be triggered if CPU > 70%. If exceeded, add another instance.
Likewise, set CloudWatch alarm if CPU drops below 30% drop and instance.

Question 23

What are Scheduled Actions Scaling Policies

Answer 23

If usage patterns are known or could be anticipated the you can set policies to automatically scale in or out based on specific time frames.

Question 24

What are auto scaling cooldowns?

Answer 24

The cool down period helps o ensure that your Auto Scaling group doesn’t launch or terminate additional instances before the previous scaling activity takes effect.

Question 25

How can you reduce costs as it relates to auto scaling cooldowns?

Answer 25

If the default cooldown period of 300 seconds is too long - you can reduce costs by applying a scaling specific cooldown period of 180 seconds to the scale-in policy.

Question 26

Your application is using an Application Load Balancer. It turns out your application only sees traffic coming from private IP which are in fact your load balancer's. What should you do to find the true IP of the clients connected to your website?

Answer 26

look into the X-Forwarded-For header in the backend

Question 27

You would like to expose a fixed static IP to your end-users for compliance purposes, so they can write firewall rules that will be stable and approved by regulators. Which Load Balancer should you use?

Answer 27

Network Load Balancer

Question 28

What does a Network Load Balancer Expose? ( public static IP or static DNS) ?

Answer 28

Public Static IP

Question 29

What does an Application Load Balancer Expose? ( public static IP or static DNS) ?

Answer 29

static DNS

Question 30

What types of Target Groups exist for ALB's?

Answer 30

``` EC2 Instances (can be managed by Auto Scaling Group) Lambda Functions (HTTP request in translated into a JSON event) ECS tasks (Managed by ECS itself - HTTP) IP Addresses - must be PRIVATE IPs ```

Question 31

Troubleshooting LBs - what are 4xx errors?

Answer 31

Client Enduced Errors

Question 32

Troubleshooting LBs - what are 5xx errors?

Answer 32

Application induced errors

Question 33

Troubleshooting LBs - what is a 503 error?

Answer 33

Instance is at capacity or there is no registered target

Question 34

If an LB cannot connect to your application what is one of the first things you should check in troubleshooting?

Answer 34

Security group rules

Question 35

Can SNI be applied to all load balancer?

Answer 35

No. Only ALB & NLB

Question 36

What is another name for connection draining?

Answer 36

Deregistration Delay

Question 37

What is the difference between simple/step scaling and target tracking?

Answer 37

Simple Scaling relies on setting a CloudWatch metric as a basis for scaling. For example, when CPU reaches 80& scale up to add 20% capacity. Step scaling builds on this by allowing you set multiple actions. Target Tracking lets you specify a scaling metric and metric value that your ASG should maintain at all times. Example CPU utilization of your EC2 should always be around 80%.

Question 38

Which load balancer(s) allow stickiness?

Answer 38

Classic and Application

Question 39

Does connection draining/deregistration delay occur on all load balancers?

Answer 39

No. Only ALB and NLB

Question 40

What is an ELB Target Group

Answer 40

A specified destination where traffic is routed to

Question 41

What is an Auto Scaling Group (ASG)

Answer 41

Contains a collection of Amazon EC2 instances
Enables you to use Amazon EC2 Auto Scaling features such as health check replacements and scaling policies.