Architecting for Scale

Chapter 8. Risk Mitigation

The mitigation column in the risk matrix is used to show what mitigations can be, or are being used to reduce the severity, the likelihood, or both values for a given risk. It is all about taking a High/High risk¹ and changing it to a High/Medium risk or a Medium/High risk.² It is not about fixing the risk, only mitigating the severity or likelihood of the risk.

As described in “Mitigation Plan”, there is a basic process that you can follow for mitigating risks. A mitigation plan details the steps you are going to take (either immediately or in the near future) in order to reduce the likelihood or severity of the risk.

Risk mitigation is knowing what to do when a problem occurs so that you can reduce the impact of the problem as much as possible. Mitigation is about making sure your application works as best and completely as possible, even when services and resources fail.

Let’s look at an example of a mitigation plan. Let’s assume that we have a database that is used for an application, such as the one described in Chapter 5. Let’s further assume that we already run the database on high-quality hardware with replicated components, such as using a RAID disk array, and server-grade redundant hardware. We believe our database is highly stable and highly available. On our risk matrix, we have the risk of a database failure as having a Low likelihood.

However, the database is still a single point of failure. If the database server fails (unlikely ...