Some sources define a compound sentence as one in which there are two independent clauses and a coordinating conjunction. The coordinating conjunctions are often referred to as the FANBOYS conjunctions because the first letters of them spell that word: for, and, not, but, or, yet, so. Your example, of course, does not have a coordinating conjunction. But it does have a semi-colon, which takes the place of a coordinating conjunction, and it does have two independent clauses. Reliable sources do describe sentences with semi-colons as compound sentences. There are three kinds of punctuation for compound sentences. The third kind is a semicolon in place of an omitted conjunction. Therefore, this is a compound sentence of the third kind.