Part 4: The downgrade & resilience — Building a 5–nines (99.999%) Available Platform

Thank you for coming back to read Part 4.

We discussed all the small nuances you need to account for in Part 3, the Math behind the 5–9’s platform in Part 2, and the context in Part 1.

Photo by Karim MANJRA on Unsplash

We will discuss interesting (and relatively easy to achieve) parts of building a 5-nines platform.

We will cheat a little here (we will take every advantage we can get) and understand the ways to keep our application working in a reasonably user-friendly way even when some services are unavailable.

We will discuss 2 main topics today — How to downgrade your application/platform APIs and How to go beyond resiliency.

Application downgrade

Imagine your application is set up for HA in this fashion, both sites are available to serve traffic based on DNS rules that are applicable to your platform. This is a happy state. You are serving your front-end application or APIs through both sites.

Now, let’s imagine, that Site 1 is down due to a region-level failure at your Cloud Service Provider, you…