WordPress offers blog services to about 10 million users. It is a true SaaS application designed with a multitenant architecture. In this architecture all users are “tenants” sharing the same database and application logic and are in virtual isolation from each other but physically in the same building. Recently WordPress had an outage which affected all 10 million users. But what was different in this scenario vis-à-vis network issues, is the outage was caused by a code change to the application.
In multitenant SaaS applications new changes are rolled out on a regular and frequent basis. Every customer is always on the latest release. However when something goes awry, everyone also gets the hit. Performance, security and service levels are all dependent of the design of the application as well as the datacenter infrastructure where the application resides.
What may be a potential solution to the ripple effect inherent in SaaS applications is a move to a “multi-apartment building” concept. In this model you have the tenants grouped into different buildings as opposed to the current model where everyone is in the same building. Using this model changes could be tested in buildings or groups of customers before being rolled out to the general population.
Having such a design would also enable testing for security vulnerabilities, specific performance enhancements and for evaluating the impact of new code changes. Therefore, when in the market for SaaS solutions, it may be wise to ask potential vendors if their application supports multiple apartment buildings or is just a single building design. You may avoid a lot of anguish in the future by making the right choice.