The Kotlin ecosystem is full of powerful tools and frameworks — and in this episode of Talking Kotlin, we’re diving deep into Exposed, JetBrains’ Kotlin SQL library, which recently reached its 1.0 release.Sebastian and Márton sit down with Chantal from the Exposed team to explore what Exposed is, where it came from, and how it helps developers work with databases in a Kotlin-first way. From type-safe SQL DSLs and lightweight DAO support to JDBC, R2DBC, Ktor, Spring Boot, migrations, and future KMP plans — this episode covers the past, present, and future of Exposed.You’ll learn:What makes Exposed different from traditional ORMsHow the DSL and DAO APIs work togetherWhy Exposed 1.0 required a major architecture redesignHow R2DBC support enables non-blocking database accessHow Exposed integrates with Ktor and Spring BootWhat’s coming next: migrations, plugins, DAO improvements, and KMP supportThe surprisingly charming origin story behind the Exposed cuttlefish mascotWhether you’re already using Exposed or just looking for a Kotlin-friendly way to work with SQL databases, this episode is packed with practical insights and behind-the-scenes stories from the team building it.Try Exposed Read the docs Join the discussion on Kotlin Slack Report issues or share feedback on YouTrack

Every time you tap through a subway gate in New York City, you’re using Kotlin Multiplatform! In this episode, we sit down with Paweł Kwieciński from Masabi to explore how they brought a decade-old Java codebase to KMP, powering ticket validation across mobile apps, embedded devices, and backend systems for public transit agencies worldwide.

Resources:

• Masabi
• J2ObjC (Java to Objective-C translator)
• Google Workspace Migration to Kotlin
• Large Scale Changes with AI – Uber | Ty Smith
• KotlinX DateTime
• Ktor (Client & Server)
• Burst library (archived)
• Java ME (Micro Edition)
• Mbed TLS
• SQLDelight
• Compose Multiplatform
• JetBrains AI Assistant & Junie

Hosts:

• Sebastian Aigner – Website | Bluesky
• Márton Braun – Website | Bluesky

Guest:

• Paweł Kwieciński

Timeline:
(0:00) Introduction
(1:12) What is Masabi?
(3:03) How does Kotlin fit into this?
(6:30) System architecture overview
(8:33) Embedded SDK and mobile apps
(10:33) Ticket inspectors and validators
(13:22) Offline operation
(16:29) The KMP decision
(24:42) Evaluating alternatives
(27:21) Planning the migration
(33:28) First lines of Kotlin
(43:45) Translating Java to Kotlin
(53:22) AI-assisted code translation
(56:39) Early AI era challenges
(1:05:01) Testing challenges
(1:08:22) KMP dependencies
(1:11:34) Domain-specific dependencies
(1:16:55) Java ME and C interop
(1:23:22) Backend-client sharing
(1:26:59) Current status
(1:31:48) Future plans: CMP
(1:36:26) Wrap-up

Sebastian and Márton talk to Vadim Briliantov, the Technical Lead for Koog: an agentic framework built by JetBrains. We learn about what AI agents are, and why building them in Kotlin with Koog is a great choice. We also discuss all the different ways AI agents can connect to other systems and your existing code, and look at advanced features for agents like custom strategies, model switching, and history compression.

Resources:

• JetBrains/koog on GitHub
• Koog Documentation

Hosts:

• Sebastian Aigner – Website | Bluesky
• Márton Braun – Website | Bluesky

Guest:

• Vadim Briliantov – LinkedIn | Medium | GitHub | Bluesky | Twitter/X

Timeline:
(0:00) Intro
(1:11) Vadim’s history at JetBrains
(4:21) What’s an AI Agent?
(5:47) Koog!
(7:12) Applications for agents
(12:43) Koog’s building blocks
(15:05) Strategies, feedback loops
(23:55) The Kotlin DSL
(26:12) Persistent state
(29:48) Subgraphs
(32:33) Tools
(39:52) MCP support (and A2A)
(44:01) Entry point and type safety
(49:39) Spring and Ktor support
(51:27) LLM Providers
(53:30) Model switching
(56:02) History and memory
(59:22) Enterprise-ready
(1:02:12) History compression
(1:11:47) Markdown?!
(1:14:37) What’s next?
(1:18:22) Going open-source
(1:20:32) Conclusion

Sebastian and Márton chat with Marcin Moskała about coroutines.

Resources:

• Coroutines Mastery course
• Coroutines | Kotlin Documentation
• kotlinx.coroutines
• Taming Asynchronous Beasts | Marcin Moskała
• Coroutine Debugging in IntelliJ IDEA | Alexey Merkulov
• Lifecycles, Coroutines and Scopes | Alejandro Serrano Mena
• Collect Like a Pro | Manuel Vivo
• Untangling Coroutine Testing | Márton Braun
• JetBrains/lincheck – Concurrent testing framework
• #talking-kotlin on Kotlin Slack

Hosts:

• Sebastian Aigner – Website | Bluesky
• Márton Braun – Website | Bluesky

Guest:

• Marcin Moskała – kt.academy

Timeline:
(0:00) Introduction
(1:18) Branding discussion
(3:23) Handling preconceptions
(4:54) What are coroutines?
(7:17) Lightweight threads?
(11:07) Where coroutines live
(13:27) Sequence Builder Example
(17:37) The design of coroutines
(20:52) What Makes Coroutines special vs other languages?
(26:56) Coroutines vs Loom
(34:55) Easy to start, hard to master
(41:07) Common mistakes
(49:33) Flows
(58:52) Thinking about Flows
(1:02:41) Derailing the conversation
(1:03:55) Flows for single values
(1:12:27) Structured concurrency
(1:18:53) The 4 advantages
(1:24:40) Seb tries web dev / The web is broken?!
(1:31:15) collectAsStateWithLifecycle
(1:32:00) Gardening break
(1:36:23) Scopes and contexts
(1:43:22) Testing coroutines
(1:50:29) Lincheck
(1:51:32) Turbine
(1:55:05) Coroutines Mastery course
(2:01:43) Wrap-up

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

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

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