Talking Kotlin

By Talking KotlinTechnology

Talking Kotlin episodes

August 11, 2025kotlinx.rpc
Sebastian and Alex chat about the kotlinx.rpc project, in a special episode recorded in the Munich JetBrains office. They explore all the different components of the library, how you can use it to define RPC services and clients, integrate with Ktor and existing gRPC definitions, and more. While the library is still experimental, it’s already feature-packed, and it has ambitious plans for the future!
kotlinx-rpc on GitHub
#kotlinx-rpc on Slack
kotlinx.serialization on GitHub
gRPC

Host: Sebastian Aigner
Website
Bluesky

Guest: Alex Sysoev
LinkedIn
GitHub
1 hr 31 min
May 15, 2025Powering TV Broadcasts Worldwide
Sebastian and Márton are joined by Denis Borisevich from RIEDEL Communications, and learn about how Kotlin is used behind-the-scenes to power media, sports, and entertainment broadcasts watched by millions around the globe. Tune in for an exciting story about how Kotlin, Ktor, and Arrow are being used in production for a use case where robust software is mission-critical.
Resources:

Riedel Communications

TornadoFX

Unsigned integer types

Arrow

Ktor

Eurovision
Hosts:

Sebastian Aigner – Website | Bluesky

Márton Braun – Website | Bluesky
Guest:

Denis Borisevich – LinkedIn
Timeline:
(0:00) Introductions
(2:42) Events powered by Riedel
(3:50) The Kotlin part
(6:44) Routing video signals
(9:12) Error handling in milliseconds
(10:31) The Kotlin part, continued
(13:29) TornadoFX!
(19:19) On introducing Compose
(23:30) Java to Kotlin migration
(26:30) Learning Kotlin after C++
(28:44) Unsigned ints in Kotlin
(32:09) Arrow!
(33:00) Server-side Kotlin
(36:25) Functional programming
(42:10) Why Kotlin over others?
(45:55) Kotlin/Java interop
(47:12) A 2-week long test suite
(51:35) Confidence in Kotlin
(53:05) Future plans
(56:00) Wrap-up
58 min
March 27, 2025Creator of Spring: No desire to write Java at All
Sebastian and Márton chat with Rod Johnson, the creator of the Spring Framework. Rod tells the story of how Spring was born more than two decades ago, and shares his recent journey of coming back to the JVM and discovering all the fun of being a newcomer to Kotlin.
Resources:

Expert One-on-One J2EE Design and Development: Rod Johnson

Oh the Places You'll Go!

Shoulders of Giants: Languages Kotlin Learned From | Andrey Breslav

Revamping and Extending Kotlin's Type System | Ross Tate

Scala in 2018 Keynote | Rod Johnson

But Java has pattern matching! | Alejandro Serrano Mena
Hosts:

Sebastian Aigner – Website | Bluesky

Márton Braun – Website | Bluesky
Guest:

Rod Johnson – Twitter | LinkedIn
Timeline:
(0:00) Intro
(0:52) The origins of Spring
(6:40) You need a business model
(8:21) Consistency is key
(9:39) Sustainable open source
(14:22) Parallels with JetBrains and Kotlin
(15:29) Rod’s journey around the JVM
(20:48) Shoulders of giants
(22:34) The newcomer experience
(24:40) LLMs write great Kotlin
(30:34) “You can start without great pain”
(33:32) Extension functions
(36:15) Too much magic?
(37:56) Rod’s feature wishlist
(39:37) Versioning and compatibility
(41:19) Ecosystems and interop
(43:34) Kotlin type system evolution
(46:27) Kotlin with Spring
(52:24) Learning Spring with Kotlin
(54:46) Kotlin in 5 years?
(1:00:39) Rod’s current work
(1:03:58) Wrap-up
1 hr 6 min
February 20, 2025Building KMP Libraries: The RevenueCat Story
Sebastian and Márton discuss building KMP libraries with Jay Shortway, the author of RevenueCat’s Kotlin Multiplatform SDK for in-app purchases.
Resources:

RevenueCat KMP SDK

How we built the RevenueCat SDK for Kotlin Multiplatform

Hybrid SDK Architecture at RevenueCat

ttypic/swift-klib-plugin on GitHub

RevenueCat/purchases-kmp on GitHub

Consider moving `Instant` and `Clock` to the standard library · Kotlin/kotlinx-datetime

RevenueCat openings
Hosts:

Sebastian Aigner – Website | Bluesky

Márton Braun – Website | Bluesky
Guest:

Joop Korteweg – Twitter
Timeline:
(0:00) Intro
(0:44) What’s RevenueCat
(4:00) In-app purchases are hard
(7:22) The multiplatform SDK
(12:44) The demand for KMP
(16:30) Hiring and team structure
(18:42) SDKs for any framework
(21:27) Building on native SDKs
(23:45) Improving iOS linking
(24:54) The SDK is on GitHub
(26:05) Benefits of building on native
(28:18) Designing a common API
(33:21) Add-on modules for SDKs
(37:30) Instant in the standard library
(38:04) Returning results from the API
(39:53) API design decisions
(44:57) Codegen opportunities
(45:48) The best things about KMP
(47:07) KMP improvements wishlist
(48:28) The KMP journey
(49:45) Wrap-up
53 min
January 23, 2025Becoming a KMP Expert
Sebastian and Pamela discuss what it means to be an expert in Kotlin Multiplatform, with the help of a panel of experts! Learn about why it's interesting to dive deep into a certain technology, recommendations on how to learn advanced topics, and general advice on how to get the most out of using KMP.
SKIE
KMP libraries:

whyoleg/cryptography-kotlin
Interesting code to explore:

JetBrains/kotlin

Kotlin/kotlinx-datetime

Kotlin/kotlinx-io

Kotlin/kotlinx.coroutines

Cartesian product by Jake

Get an invite!
Ecosystem wishlist:

wasmJs support in SQLDelight

Compose Multiplatform support in MapLibre
Learning resources:

Kotlin Multiplatform build setup from scratch with Sebastian Sellmair

KEEP - Kotlin Evolution and Enhancement Process

HexFormat proposal and discussion

Uuid proposal and discussion
More KMP experts:

Kevin Galligan

Bluesky

Twitter

Russell Wolf

GitHub

Twitter

multiplatform-settings

Jesse Wilson

GitHub

Sebastian Sellmair

Twitter

Salomon Brys

Twitter
Hosts:

Sebastian Aigner

Website

Pamela Hill

Blog

Bluesky
Guests:

Jake Wharton

Website

John O'Reilly

Website

KMP samples on GitHub

Konstantin Tskhovrebov

Mastodon

Tadeas Kriz

Mastodon

Bluesky
(0:00) Introductions
(1:40) Why be a KMP expert?
(9:14) First steps to being an expert
(16:38) Respecting each platform
(24:04) Libraries for KMP
(27:45) Advanced learning resources
(38:18) Ecosystem wishlist
(43:03) Exercising your KMP skills
(48:15) Shoutouts to other experts
(51:34) Wrap-up
53 min
December 09, 2024Going from Swift to Kotlin with Skip
In a slightly unconventional episode, Sebastian and Márton talk to the founders of Skip, an iOS-to-Android, Swift-to-Kotlin transpiler solution. Marc and Abe have a background working on both Apple platforms and the JVM, and their latest project is a bridge across these two ecosystems.
Skip
Skip.tools on GitHub
Contributing to SkipUI webinar
kdoctor
Hosts:
Sebastian Aigner
Website
Bluesky
Márton Braun
Website
Bluesky
Guests:
Abe White
Twitter
Mastodon
Marc Prud'hommeaux
GitHub
(0:00) Weather
(2:02) Introductions
(3:10) ⁠Elevator pitch⁠
(3:45) The initial idea
(6:14) Pivot around the server-side
(8:35) Skip(.tools)
(8:56) The target audience
(9:58) What about Android devs?
(12:11) The current state
(14:57) Pricing and components
(16:43) ⁠Contributing to SkipUI⁠
(18:55) Reimplementing everything
(23:07) ⁠The Skip stack⁠
(26:17) Wrapping JVM types
(28:27) Writing Kotlin in Swift?!
(29:56) Tooling support
(32:02) There’s a Gradle project!
(34:39) iOS API coverage
(38:24) Platform differences
(40:10) Data storage
(44:31) Building on JVM libraries
(46:42) JSON problems
(48:00) Testing the Skip stack
(51:42) SwiftUI to Compose
(58:21) IDE experiences
(1:03:35) Conclusion
1 hr 5 min
November 21, 2024Platform Integrations in Kotlin Multiplatform with Russell Wolf
Sebastian introduces the new co-host of the podcast, in a special episode recorded on location at droidcon New York! Joined by Russell Wolf, author of the multiplatform-settings library, we discuss the conference, different code sharing approaches for Kotlin Multiplatform, and how to build great multiplatform libraries.
droidcon New York
When sharing isn’t caring: Using platform-specific code in Kotlin Multiplatform (Russell’s talk)
Compose Multiplatform on iOS: On the Road to Stable (Seb’s talk)
Composing an API the *right* way (Márton’s talk)
The deprecated Accompanist WebView implementation for Jetpack Compose
russhwolf/multiplatform-settings on GitHub
Kotlin Multiplatform database libraries
Room
SQLDelight
Dependency injection libraries
Koin
Kotlin-inject
ViewModel for Kotlin Multiplatform
Hosts:
Sebastian Aigner
Website
Márton Braun
Website
Guest:
Russell Wolf
GitHub
Twitter
Timestamps
0:00 Intro at home
2:02 Intro at droidcon NYC
4:23 Russell’s talk topic
8:14 Code sharing approaches
12:28 Wrapping native APIs
16:18 Attempted segue
16:35 Designing reusable APIs
18:02 Actual segue
18:14 multiplatform-settings
20:23 Supported platforms
24:05 SharedPreferences challenges
26:20 Observable preferences
29:51 Secure storage
30:55 Windows again
31:36 Library code as reference
33:15 Testable library code
35:05 Initializing a KMP library
38:18 Database libraries
40:55 Dependency injection
44:40 Outro
46 min
August 29, 2024 Kotlin After 2.0
In this episode, we talk about the future of Kotlin and its development after the 2.0 version.
1 hr 7 min
July 03, 2024 Reinventing Ticket Sales with Pretix
In this episode of Talking Kotlin, Hadi Hariri and Sebastian Aigner chat with Raphael Michel, the founder of pretix, an open-source ticketing system. Raphael shares his fascinating journey, from building pretix to solve a conference ticketing problem to becoming a full-fledged company with a global reach.
The conversation dives into the complexities of event ticketing, the challenges of the pandemic, and the surprising new markets pretix entered, like managing access for public swimming pools in Berlin.
Throughout the episode, Raphael discusses how Kotlin plays a crucial role in pretix's development. He talks about using Kotlin for various components, including Android apps, desktop applications, server-side logic, and even future plans for integrating with hardware like turnstiles.
50 min
June 12, 2024 Kord: Deep Dive into the Discord API
Join us for an in-depth conversation with Michael Rittmeister and Luca Kellermann, the brains behind Kord, a Kotlin library designed for interacting with the Discord API. In this episode, we dive into the complexities of the Discord API, the importance of WebSockets, and the challenges and strategies in building and maintaining a modularized library. We also explore the future of Kord, including their move towards native support and the ongoing effort to keep up with Discord's evolving features. Whether you're a Kotlin enthusiast or a Discord bot developer, this episode is packed with valuable insights and practical advice.
Kord library – https://github.com/kordlib/kord
Michael on X – @SchlaumeierTVDE
Luca on GitHub – https://github.com/lukellmann
47 min