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Although the MUC terminal is big and you're likely to have a walk, there are small, free hand-carts for your carry-ons.

Also, there's an Dallmayr coffee shop in the domestic terminal, right at the entrance to the concourse. They have wonderful coffee, pastry, and chocolate. (I recommend picking up a pound of coffee to bring home.) There's also a food court in the same area. As I recall, the snacks are pretty good, although somewhat expensive.

http://www.munich-airport.de/en/cons...stro/index.jsp

A ninety-minute layover will be plenty, unless the incoming flights are late. However, that's no different from any other airport where you're making an international connection, and Munich is easier to transit than Frankfurt.

I hope you have a great trip!