Incredibly slow performance on SELECT query (and its corresponding EXPLAIN), works fine on MySQL

With a very, very small dataset (less than 1KB of actual data), a SELECT query takes several minutes. The EXPLAIN query takes just as long, leading me to believe it is an optimiser bug. On MySQL 5.5.33 it [the EXPLAIN query] takes 0.00s. On MariaDB 5.5.33 it takes an eternity (also tried on latest stable 5.x and 10.x versions, 5.5.38 and 10.0.12 at the time of writing). This is with the highly reduced testcase I'm including. With my actual dataset (still quite small less than 1MB in total table sizes according to phpMyAdmin), I killed the EXPLAIN query after 6 HOURS!

Admittedly, the query has a redundant join in it, which I removed and it fixed the problem I was experiencing, but I think this is a bug anyway.