I found the role through a third-party headhunting firm.
I was given a take-home assignment to complete, which I submitted in a week. However, I heard no feedback from the company for another 10 days, despite a few follow-ups.
I eventually heard that Duolingo decided to pass, with no given reason, apparently "per company policy". This was very puzzling and frustrating, as I spent a good amount of time polishing up the project and couldn't even get a canned, cut-and-paste response as feedback.
Side-note: they supposedly offer $500 to candidates who complete the take-home project, but the processing has been very slow, once again despite follow-ups.
Take-home project
The following metrics were computed from 2 interview experiences for the Duolingo iOS Engineer role in New York, New York.
Duolingo's interview process for their iOS Engineer roles in New York, New York is extremely selective, failing the vast majority of engineers.
Candidates reported having very negative feelings for Duolingo's iOS Engineer interview process in New York, New York.