AWS System Design for High Availability (Part 2)

Part 1, Part 2

Introduction

From the first part, we learnt about what high availability (HA) is and Elastic Load Balancing (ELB). This time we will talk about Amazon Route 53 and connection to components outside of AWS.

Route 53

If you remember, last time we talked about HA across different AZs. However, some of you may wonder that is it possible to do HA across regions? For example, in case a country is under disaster and no AZ can be used. In this situation, we want to failover to different region. Thanks to Route 53, we can implement this solution.

As the name indicated, 53 means port 53, it is an authoritative DNS service from AWS. It is able to translate domain names into IP addresses.

Above shows the most simplest example of how Route 53 works.

Benefits of Route 53 are listed as below:

  • Reliable. It has redundant locations and backed with 100% SLA
  • Easy to use. It has console and programmatic API with domain name management.
  • Fast. It is worldwide anycast network and fast propagation of changes.
  • Cost-effective. It has inexpensive rates and pay-as-you-go model
  • Integrated with AWS. It can support ELB-Alias queries and latency-based routing.
  • Flexible. It is geolocation routing and self-aliasing.

In order to improve availability of our applications running on AWS, we are able to configure backup and failover scenarios for our own applications. Also, we can enable high available multi-region architectures on AWS. Finally, we can improve health check by combine multiple health check e.g. domain name based health check, string matching and so on.

Above is an example of multi-region deployment.

In some cases, we may not want our website totally down. Then the secondary path will point to the static website hosting on S3. Once the primary path is not available, then it will failover to the static web site. Even though the some functions may not work, we can at least show something to our customers.

Some companies will use the above situation for HA. It does not only apply on application, but also the email servers.

Connections to Components Outside of AWS

As mentioned in my previous articles, we can use AWS direct to connect single router and dual ports.

Conclusion

Now we learn the system design for HA. In fact, there are two main services: ELB and Route 53. Generally speaking, ELB is for AZ HA while Route 53 is for region HA.

Leave a Reply