Optimistic UI — Fullstack

Discovery

Infer from context before asking:

1. Data fetching library? — React Query, SWR, RTK Query, tRPC, or raw fetch with local state?
2. What's being mutated? — list item (add/delete/reorder), field update, toggle, or form submit?
3. Is ordering or ID generation involved? — optimistic items need a temporary ID strategy
4. What should happen on failure? — silent rollback, toast, inline error, or retry prompt?

The Three Failure Modes to Design For Upfront

Most implementations only handle the happy path. Design all three before writing code: