How Major Metros Run on KMP
From Talking Kotlin by Talking Kotlin
March 5, 2026 · 1h 39m · Season 1 · Episode 145
About this episode
This episode explores how Masabi transitioned a Java codebase to Kotlin Multiplatform for public transit ticket validation.
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…
People in this episode
Hosts: Sebastian Aigner, Márton Braun
Guest: Paweł Kwieciński
Topics covered
- Kotlin Multiplatform
- public transit
- software migration
- ticket validation
- embedded systems
- mobile apps
Keywords
- Kotlin
- Masabi
- public transit
- KMP
- software migration
- ticket validation
- embedded devices
- mobile apps
Mentioned in this episode
Organizations: Masabi, JetBrains
Products: Kotlin Multiplatform, J2ObjC, KotlinX DateTime, Ktor, Burst library, Java ME, Mbed TLS, SQLDelight, Compose Multiplatform, AI Assistant
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