Quizlet Adopting Kotlin Multiplatform

Published 2019-12-18

@kpgalligan shared Quizlet's Medium post, Shared Code at Quizlet: Deciding on Kotlin Multiplatform, the day it dropped.

I then discovered @ankushg had already let that cat out of the bag nearly 2 months earlier:

Tweet by Ankush Gupta including the sentence: "We also use Kotlin Multiplatform to share business logic across iOS (Native), Web (JS), and ofc Android"

It's a super interesting read because it tells the story of trying to share with JavaScript first, thinking about sharing with C++, then finally deciding on Kotlin Multiplatform.

I'm a fan of the term "platform citizen" but it's probably a coincidence that they used it too:

Kotlin Multiplatform promises the ability to write code in Kotlin and have it run as a first-class citizen on each platform.

But here are my favorite takeaways:


For many businesses, requiring internet connectivity for core product features might be a very reasonable requirement! Quizlet however has a particularly strong affinity for mobile users with limited Internet access. ... By focusing our shared code efforts on code based around state management and control flow, we saved our engineering team countless person-hours with minimal time spent on cross-platform threading or concurrency concerns.


these issues resulted in an ecosystem where frontend web developers might have felt comfortable writing shared code, but mobile developers certainly did not feel comfortable consuming it. ... We were able to write our most critical business logic in one place, ship it across multiple platforms, and unblock our resource-constrained native mobile teams. Most importantly, we were able to do this without committing to writing our entire client with the same framework.

Kotlin Multiplatform

even our frontend web engineers found themselves impressed by Kotlin. ... In early 2019, Quizlet migrated all of our shared code over to Kotlin Multiplatform, and we are using it in production to serve over 50 million monthly active users.

Please read the whole thing: Shared Code at Quizlet: Deciding on Kotlin Multiplatform

And check out their mention in the KotlinConf Keynote alongside a several other great examples of Kotlin Multiplatform in production

Skip to 13:00 for Mobile Multiplatform mentions

This post originally written for Touchlab