Measuring System Complexity

I think we can all agree that the less complex our systems are, the easier they are to modify, operate and troubleshoot. But how can we properly measure complexity?

The most popular answer will be something related to cyclomatic complexity or number of code lines. But have you ever tried to use them in practice? I found them absolutely impractical and not actionable for huge codebases. They will always show you some numbers detecting the system is big and complex. Nothing new actually 🙃

I found more practical alternatives in Google SRE book:
🔸 Training Time: Time to onboard a new team member to the team.
🔸 Explanation Time: Time to explain high-level architecture of the service.
🔸 Administrative Diversity: Number of ways to configure similar settings in different parts of the system.
🔸 Diversity of Deployed Configurations: Number of configurations that are deployed in production. It can include installed services, their versions, feature flags, environment-specific parameters.
🔸 Age of the System: The older system tends to be more complex and fragile.

Of course, these metrices are not mathematically precise, but they provide high level indicators of the overall complexity of the existing architecture, not just individual blocks of code. And most importantly, they show what direction we should take to improve the situation.

#engineering #systemdesign