Does memcached send packets that fragment on IP layer using UDP and not TCP?

Question

question is in title.

I have read that memcached fragments only on application layer for large responses. Is this always the case? If TCP is not used e.g. client -> a.b.c.d:UDP/11211 ; a.b.c.d:UDP/11211 -> client, how can the memcached server know the PathMTU to ensure that there is no IP-Fragmentation?

Does it silently check the path with PMTUD and TCP?

Thanks in advance, The Dude