Design (in Object Oriented manner) a restaurant reservation service. No coding necessary beyond class names and method names and rough description of how they work. Then design the SQL database for this system (table names, columns and foreign keys)
I was asked the question about ACID implementation in C#. Also was given a problem described as pretty typical for that company and asked how to deal with that model. The overall problem was about gathering feeds and transforming them into a data via ETL engine to multiple databases.
Pros: ability to step through on code level, one can query almost any type of data as long as it is implementing either IQueryable or IEnumerable. Cons: one needs to be aware of how the SQL statement is constructed (make sure there are no unnecessary joins, etc. created).
There is an assumption that the array does not have holes (1,2,3,4,5 vs 1,3,5,6,7,9) judging by the comment that only one number is skipped. But they don't say it outright. They don't give you much paper space, and they expect you to write the code in pencil.