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  1. Meet a Duo: Caesar Wirth, Senior Software Engineer

    Meet Caesar, a Senior Software Engineer at Duolingo. After five years in Japan, Caesar recently moved to Pittsburgh to be closer to the Duolingo team. In this interview, we speak to Caesar about what he works on at Duolingo, what he thinks of Pittsburgh compared to Tokyo, and what he does for fun outside of work.

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  2. Meet a Duo: André Kenji Horie, Senior Software Engineer

    Meet André Kenji Horie, a Senior Software Engineer who has been at Duolingo for three years. André came all the way from Brazil to Pittsburgh, with a few years in Tokyo in between. We asked André about where he's from, what it's like to work at Duolingo and what he thinks about living in Pittsburgh.

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  3. Rewriting Duolingo's engine in Scala

    Recently, we profoundly refactored the engine that drives Duolingo lessons. This post talks about our engineering choices, experiences, and the pain points of rewriting a highly complex system.


    • Redesigned architecture
    • Refactored code from Python to Scala
    • Latency dropped from 750ms to 14ms
    • Engine uptime increased from 99.9% to ...

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