Feature toggles (sometimes referred to as feature flags) are an engineering practice aiming to control application behavior without the need to deploy a code change. The behaviors that toggles can affect range from hiding under development features, limited feature release (canary) to a subset of users, or used to switch to fallback implementation in the event of a system issue, and more.

In the previous architecture spotlight entry, we discussed Event Sourcing and illustrated the concept with a simple banking account example. We laid out many of its pros and cons to help readers decide if the pattern would be useful to them.

Software architecture is the analysis, thought and design considerations that form the foundational scaffolding for a successful software system. If you write software for work or as a hobby, whether you know it or not, you’re already dealing with software architecture and the processes of making architectural decisions within your applications.

Event sourcing is a powerful architectural pattern that records all changes made to an application’s state, in the sequence in which the changes were originally applied. This sequence serves as both the system of record where current state can be sourced from, as well as an audit log of everything that happened within the application over its lifetime.

In 2007, we were invited to speak at the Apple WWDC event. At the time we didn’t know why we were invited.