Deployment & Provisioning

Question 1

What are the two commons for EC2 instances failing?

Answer 1

#InstanceLimitExceed error - Exceeded the default limit for number of instances on a region, can add more.
#InsufficientInstanceCapacity error - Aws do not have currently enough available EC2 on-demand for your request.

Question 2

What is a Bastion Host/Jump Box?

Answer 2

Bastion host is server connected to a public subnet, can connect via internet and gives access to the private subnet through SSH/RDP only.

Question 3

What is the layer that Application LoadBalancer, Network Load and Classic Load Balancer

Answer 3

# ALB: Layer 7 Application
# NLB: Layer 4 transport
# CLB: Layer 7 and 4, but 7 is limited

Question 4

What is Application Load Balancer?

Answer 4

Is for HTTP and HTTPS, and is application-aware(know about the route, path and etc), routing based on request.

Question 5

What is Network Load Balancer?

Answer 5

Is for TCP traffic, extreme performance, handle millions of request per second.

Question 6

What is Classic Load Balancer?

Answer 6

Is legacy ELB, can handle HTTP/HTTPS, use X-Forwarded and sticky sessions for routing, or use only TCP

Question 7

What is Pre-warming an ELB?

Answer 7

Avoid overloading the ELB, contact AWS support and specify req/s is expected, range of time, total size of a typical request.

Question 8

An Application is behind an ELB and needs Static IP/ Elastic IP what ELB choose and Why?

Answer 8

Network load balancer because NLB creates static IP for each subnet.

Question 9

What are erros 4XX that ELB returns?

Answer 9

# 400 - Bad/malformed request
# 401 - Unauthorized use access denied
# 403 - Forbidden request is blocked by WAF acces control list
# 460 - Client closed connection before load balancer could respond, client timeout may be short.
# 463 - Load balanacer receive an X-Fowarded-For request header with > 30 IP addresses

Question 10

What are erros 5XX that ELB returns?

Answer 10

# 500 - Internal error server.
# 502 - Bad gateway application server closed the connection/ malformed response
# 503 - Service Unavaible - no registered target
# 504 - Gateway timeout app is not respoding
# 561 - Unauthorized received an erro code from the ID provider.

Question 11

What are different types of metrics of ELB?

Answer 11

# General health - HealthyHostCount/UnHealthyHostCount, HTTPCode_Backend_2XX /3XX / 4XX / 5XX
# Performance - Latency, RequestCount, (SurgeQueueLength and SpilloverCount(Classic only)) --> high number is perfomance issues