Load Balancer

Question 1

AWS has 4 kinds of managed load balancers what are they

Answer 1

Classic Load Balancer
Application Load Balancer
Network Load Balancer
Gateway Load Balancer

Question 2

What does the Classic Load Balancer support

Answer 2

HTTP
HTTPS
TCP
SSL

Question 3

What does the Application Load Balancer support

Answer 3

HTTP
HTTPS
Websocket

Question 4

What does the Network Load Balancer support

Answer 4

TCP
TLS
UDP

Question 5

What does the Gateway Load Balancer support

Answer 5

IP Protocol (Operates on layer 3)

Question 6

What are some features of Application Load Balancer

Answer 6

Load Balancing to multiple HTTP applications across machines (target groups

Load Balancing to multiple applications on the same machine (containers). Fits with ECS well cuz ECS has dynamic port mapping

Supports redirects. Ex: Can redirect HTTP to HTTPS

You can also write routing rules for path, headers, query string etc

Target groups can be (EC2s, ECS tasks, Lambdas, or IP addresses)

ALB can route to multiple target groups and has health checks at the target group level

Question 7

What are some features of Network Load Balancer

Answer 7

All to forward TCP and UDP traffic to your instances
Handle millions of requests per second
Less latency

It has one static IP per AZ and supports assigning Elastic IP

NLB are used for extreme performance

Target groups are (Ec2s, Ip addresses or ALBs)

Resolving Regional NLB DNS name returns the IP addresses for all the NLB nodes in the AZs

Resolving Zonal DNS Name: so it returns the ip address of one specific AZ

Question 8

What are some features of Gateway Load Balancer

Answer 8

Deploy, scale and manage a fleet of 3rd party network virtual appliances like Firewalls, Intrusion Detection, Packet Inspection

Operates at Layer 3 (Network Layer) - IP Packets

So it is useful if you want to scan your traffic before it reaches your application. Here your target group will be your 3rrd party virtual appliances

Target groups (EC2s, IP addresses)

Question 9

Explain Cross Zone Load Balancing

Answer 9

With Cross Zone Load Balancing, each load balancer distributes evenly across all registered instances in all the AZ. So if you have 2 instances in one AZ, they get 10% each, and if you have 8 in another, they get 10% each

Question 10

What happens if you dont have Cross Zone Load Balancing

Answer 10

Without Cross Zone Load Balancing, each load balancer distributes evenly across all registered instances in just their respective AZ. So if you have 2 instances in one AZ, they get 25% each, and if you have 8 in another, they get 6.25% each

Question 11

Which Load Balancers have Cross Zone Load Balancing enabled

Answer 11

Only the Application Load Balancer has Cross Zone Load Balancing Enabled by default and it cant be disabled

Both CLB and ALB wont be charged for inter AZ data if enabled

Gateway & Network will be charged for inter AZ data if enabled

Question 12

Which load balancers implement sticky sessions (session affinity)

Answer 12

Both CLB and ALB

Question 13

Which load balancers implement Least Outstanding Requests

Answer 13

Both CLB and ALB

Meaning the next instance to receive the request is the instance that has the lowest number of pending unfinished requests

Question 14

Which load balancers implement round robin request routing algorithm

Answer 14

Both CLB and ALB

Question 15

Which load balancers implement Flow Hash request routing algorithm

Answer 15

NLB

Selects a target based on the protocol, source/destination IP address, source/destination port and TCP sequence number