This section covers the following official AWS Certified SysOps Administrator – Associate (SOA-C02) exam domains:
Domain 2: Reliability and Business Continuity
Domain 5: Networking and Content Delivery
If you can correctly answer these questions before going through this section, save time by skimming the Exam Alerts in this section and then completing the Cram Quiz at the end of the section.
1. You have deployed a set of 10 EC2 instances with the intention to make your application highly available. Your instances have been evenly deployed into us-west-2a. You would like to use the Network Load Balancer to make the application highly available. What would be the result of this configuration?
2. You have been asked to ensure your application is able to withstand a regional outage. Which service can be used in AWS to load-balance traffic between two regions in a 50–50 percent fashion?
1. Answer: Deploying the instances in only one availability zone (us-west-2a) is not optimal because it would make the application highly available but not resilient to an availability zone outage. Deploy the instances into two availability zones in us-west-2.
2. Answer: Route 53 with weighted routing would be the correct solution to allow for sending traffic to both regions. Because 50–50 is required, both region endpoints need to be added to the weighted record with equal weights.
One of the key AWS services that enables you to deploy highly available applications is the Elastic Load Balancing (ELB) service. ELB integrates with EC2, ECS, EKS, and other AWS services and enables you to distribute traffic across multiple instances of your application for high availability. The ELB service can also work together with the AutoScaling service to enable higher resilience of your application. When a failure occurs, the AutoScaling service can automatically scale the number of instances to meet the traffic demands that were previously handled by the file instance(s).
Four types of load balancers are available in AWS:
Classic Load Balancer
Application Load Balancer (ALB)
Network Load Balancer (NLB)
Gateway Load Balancer (GLB)
ELB Classic is the previous-generation load-balancing service that still provides a robust and simple-to-use load balancer to forward traffic to one or more availability zones within a region. ELB Classic is also supported on the EC2 Classic network. Neither one of these services is intended for use with modern, highly available, resilient architectures, and they are provided at this point merely for backward compatibility. Most modern applications should be designed to use the ALB or NLB service because the plan is to retire the Classic Load Balancer in August 2022.
The ALB is the next-generation layer 7 load-balancing solution from AWS that can handle HTTP and HTTPS traffic. The service can understand the application request, and based on the pattern of the request, can route the request to multiple back ends. This capability is useful when running microservices or other distributed solutions within an application. The ALB service automatically handles high availability of the service by deploying a redundant endpoint in each availability zone that it serves, with a minimum of two.
The NLB is the next-generation layer 4 load-balancing solution from AWS that can handle TCP, UDP, and SSL/TLS traffic.
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