The short answer
Hotel restaurants stay open, but many local restaurants and small shops close. Eid al-Fitr, the feast ending Ramadan, is expected about 9 to 10 March 2027 and closes many small places for the two holiday days. Eid al-Adha, expected about 16 to 17 May 2027, closes most non-hotel restaurants for several days.
In more detail
Eid al-Fitr marks the end of Ramadan. Families gather, children get new clothes and the sweets come out. It brings two public-holiday days, when many small shops and local restaurants close and transport is busy as families travel home. Hotel restaurants carry on, and it is worth asking your riad what it will serve.
Eid al-Adha, the Feast of the Sacrifice, is the bigger closure. Each family has its sheep, and it is the year's biggest family gathering. Most non-hotel restaurants and many shops close for days, and buses and trains are packed. It is a poor week for a trip focused on medina food and shopping.
Both dates follow the moon, so they can shift by a day. If your trip overlaps, eat where you sleep, book riad dinners ahead and plan day trips into the countryside rather than a souk-and-street-food week.
The upside is seeing a Moroccan holiday from inside. If your riad family invites you to share sweets or tea, accept.