How to improve ajax update ? JSF performance

Question

I am developing a system for restaurant and I have a datagrid that updates the other.
For example: I click on the class and update the product datagrid.

It works, but the result is slow.

I’m wearing a <h:commandLink> with update:

<p:commandLink  actionListener="#{mesaControle.setClasseFiltro(grupo)}"
                action="#{mesaControle.validaBuscarProduto()}" 
                update="form:produtos">
    <button style="background-color: #0b66b1; height: 55px; width: 100px;">
    <br/>
    <strong style="color: #f6f6f6">#{grupo.nome}</strong></button>
</p:commandLink>

And filter as follows:

public List<Produto> listaClasse(Classe produtoFiltro) {
    Query q = em.createQuery("FROM Produto As a WHERE a.classe = :para order by id asc");
    q.setParameter("para", produtoFiltro);
    return q.getResultList();
}

---

Everything works perfectly, but the performance leaves to be desired.
How can I improve performance?