MobX

MobX tracks observable reads and updates dependents automatically when actions mutate state. Mental model: transparent reactive programming on mutable domain objects — contrast with Redux's explicit event log.

Subtopics: observables, actions, computed values, reactions.

On interviews: explain dependency tracking vs manual selector subscriptions; when mutable models improve ergonomics.

Common pitfalls: untracked reads outside actions, reaction feedback loops, and observables without clear action boundaries.

Checklist:

• Mark state observable explicitly.
• Mutate inside actions.
• Derive with computed, side effects with reactions.
• Use observer components for granular updates.