Implement an autocomplete request optimizer for a mobile search box. Given a list of timestamped query updates, return the timestamps and query strings that should trigger an API call. A call should only be sent if the user has stopped typing for debounce_ms, the query length is at least min_length, and the same query has not been sent within the last cache_ttl_ms.
def optimize_autocomplete(events, debounce_ms, min_length, cache_ttl_ms):