Autocomplete search bar with a hand-written debounce

Build an autocomplete search bar: as the user types, show suggestions for the current text, fetched from a suggestion service. Calls must be debounced, so the service is called only after the user pauses typing, and you write the debounce yourself rather than using a library. Discuss responses arriving out of order, empty input, loading and error states, and keyboard and screen-reader access.