What happens when you dispatch an action?
Interviewer Expectations for this Question
01
Core Competency
Assesses fundamental understanding of React conventions, runtime behavior, and memory/performance considerations.
02
Evaluation Criteria
Hiring managers look for precision, avoidance of ambiguous jargon, and ability to explain trade-offs under real production conditions.
Comprehensive Model Answer
Verified Solution
store.dispatch(action)is called with a plain action object ({ type, payload }).- The action passes through the middleware chain in order (e.g., logger → thunk → your custom middleware); async/thunk middleware may intercept it here (e.g., a thunk function is invoked instead of being forwarded, or a Promise/generator is handled) or asynchronous side-effects can trigger further dispatches later.
- Once every middleware calls
next(action), the action reaches the root reducer. - The root reducer (usually built with
combineReducersor RTK'sconfigureStore) forwards the action to every slice reducer, each returning either its unchanged state or a new state object. - The store replaces its internal state tree with the combined result and marks the update complete.
- The store notifies all subscribers (React-Redux's
Provider/useSelectorinternals) that state changed. - Each connected component's selector is re-run and compared (via
===or a custom equality function) against its previous result; components only re-render if their selected slice actually changed.
Candidate Response Strategy & Interview Tips
- Start with a concise one-sentence summary: Deliver a direct, confident answer first before expanding into nuances.
- Demonstrate real-world trade-offs: Discuss where this approach excels and when you would avoid it in production systems.
- Discuss complexity & edge cases: Proactively explain time/space complexity or boundary conditions (null values, scale limits).
- Prepare for interviewer follow-ups: Technical hiring panels frequently probe deeper into concurrency, backward compatibility, or alternative libraries.