The React Compiler Just Made Your Memoization Knowledge Obsolete. Here’s What to Learn Instead.

React Compiler v1.0 (stable since October 2025) automates memoization more precisely than manual use of useMemo, useCallback, and React.memo — including cases those hooks can't reach. The post explains exactly how the compiler works at the source level, identifies the three remaining cases where manual memoization is still justified (third-party referential equality, try/catch blocks, explicit useEffect dependency control), and provides a step-by-step migration guide for enabling the compiler and removing unnecessary hooks. It argues that React expertise now shifts from render-cycle optimization to architectural concerns: server/client boundaries, component composition, and data flow design.