The vast majority of challenges, bugs, complexity, and performance issues in software engineering can be reduced to managing state. State is hard. Immutable sta

The vast majority of challenges, bugs, complexity, and performance issues in software engineering can be reduced to managing state. State is hard. Immutable state solves a lot of these issues in theory, but in practice mutable state is the tradeoff you must make in many cases to get acceptable performance. The cost of this tradeoff is the increased complexity cost. A good engineer understands the sweet spot of these tradeoffs. Use functional techniques with immutable data structures in the right places where performance is unlikely to become an issue.