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Version: 1.0

Elastic Load Balancer

  • Route the traffic to your instances that are healthy
  • Must have at least two Availability Zone
  • Cannot go cross-region. You must create one per region
  • Can attach Amazon Certification Manager SSL to any ELB for SSL

Application Load Balancer​

  • Operates on the layer 7 of OSI model
  • Listener: checks for connection requests from clients, using the protocol and port you configure
  • Rule
  • Target Group
  • Target
  • Supports only HTTP, HTTPS and WebSocket

Network Load Balancer​

  • Operate at layer 4
  • Use where we need extreme performance
  • Other use cases are where you need protocols not supported by Application Load Balancers
  • It can decrypt traffic, but you will need to install the certificate on the load balancer
  • Support TCP and HTTP health check

Classic Load Balancer​

  • A 504 error means the gateway has timed out
  • Need the IPv4 address of your end use: look for the X-Forwarded-For header

Sticky Sessions​

  • Allow to bind a user's session to a specific EC2 instance

X-Forwarded-For​

  • Allow to determine users IP
  • X-Forwarded-For: get IP address
  • X-Forwarded-Port: get the port
  • X-Forwarded-Proto: get the protocol

Registration Delay​

  • Allows load balancer to keep existing connection open if the EC2 instance are de-registered or become unhealthy

Health Checks​

  • Communicates with instances to determine their state
  • ELB does not terminate (kill) unhealthy instance. It will just redirect traffic to healthy instance

Cross-Zone Load Balancer​

  • Each Load Balancer instance distributes evenly across all registered instances in all AZ
  • ALB
    • Enabled by default (can be disabled at The Target Group level)
    • No charges for inter AZ data
  • NLB and GLB
    • Disabled by default
    • You pay charges for inter AZ data if enabled
  • CLB
    • Disabled by default
    • No charges for inter AZ data

Auto Scaling Group​

  • Scale out (add EC2 instances) to match an increased load
  • Scale in (remove EC2 instances) to match a decreased load