Here you can find sample exams from previous years. Most of the exams are from PADI, a course that preceded DAD and had many topics in common.
Note that, each year, the content of the exam is adjusted to the topics actually covered in the classes. For instance, this year, we did not cover concurrency control and transactions, thus no questions about these topics will appear in the exam. On the other hand, we did cover consensus/paxos with more detail, so questions about this topic may (or may not) appear in the exam.