public Materialized<K, V, S> withKeySerde(final Serde<K> keySerde) {
        this.keySerde = keySerde;
        return this;
    }
Set the keySerde the materialized {@link StateStore} will use.
@param keySerde  the key {@link Serde} to use. If the {@link Serde} is null, then the default key
                 serde from configs will be used
@return itself
streams/src/main/java/org/apache/kafka/streams/kstream/Materialized.java