Based on comments above, I: 1) Turned on google search history 2) searched for 'python lambda syntax' and 'mutex lock' 3) got the invite that opened the foo.bar

Based on comments above, I: 1) Turned on google search history 2) searched for 'python lambda syntax' and 'mutex lock' 3) got the invite that opened the foo.bar UI You get a terminal, from the terminal you request coding challenges. They have a minimal IDE to code in. Choice of language is Java or python. Only tried one challenge. YMMV