convex-svelte realtime by default.

const messages = usePaginatedQuery(
  api.messages.paginatedList,
  { searchWords: [] },
  { initialNumItems: 3, keepPreviousData: true }
);

// optimistic send: shows instantly, reconciles on server confirm
client.mutation(api.messages.send, { author, body }, {
  optimisticUpdate: (store) => {
    const first = store
      .getAllQueries(api.messages.paginatedList)
      .find((q) => q.value && q.args.paginationOpts.cursor === null);
    if (!first?.value) return;
    store.setQuery(api.messages.paginatedList, first.args, {
      ...first.value,
      page: [{ author, body, optimistic: true }, ...first.value.page]
    });
  }
});