Ryz Labs/Hire/MobileHire senior Kotlin developers for Android and the backend
Senior Kotlin engineers for Android apps, JVM services and Kotlin Multiplatform, vetted by Ryz and embedded in your team within ±1h of US time zones.
By the Ryz Labs team · Updated October 2026
Hiring Kotlin developers through Ryz gets you senior engineers who write idiomatic, concurrent Kotlin, whether that means an Android app, a Spring Boot or Ktor service, or shared logic with Kotlin Multiplatform. They are in the top 1% of the candidates we interview, and they join your team as embedded members working within ±1h of US time zones.
What our Kotlin developers work on
Kotlin started on Android but now runs a lot of server code and shared mobile logic. Our Kotlin engineers usually fall into one of three tracks, and many cross between them: Android apps, JVM backends, and Multiplatform projects that share code between Android, iOS and the server.
- Android apps: Jetpack Compose UIs, coroutine-based data layers and modular Gradle builds.
- Kotlin Multiplatform: shared networking, persistence and business rules for Android and iOS using Ktor client, SQLDelight and kotlinx.serialization, with Compose Multiplatform where it fits.
- Spring Boot services in Kotlin: REST and gRPC APIs, Spring WebFlux with coroutines, and data access through Spring Data or Exposed.
- Ktor backends: lightweight services with Ktor server, structured logging and OpenTelemetry tracing.
- Java to Kotlin migrations: converting legacy Java code module by module while keeping interop clean.
- Event-driven systems: Kafka consumers and producers written with coroutines and Flow.
Skills we vet for
- Idiomatic Kotlin: data and sealed classes, extension functions, scope functions used with restraint, and expressive null handling.
- Coroutines and Flow: structured concurrency, dispatchers, cancellation, exception handling with supervisors, and cold versus hot flows.
- Type system: generics with variance, reified type parameters, inline and value classes, and contracts.
- Java interop: platform types, @JvmStatic and @JvmOverloads, and calling Kotlin cleanly from Java code.
- Multiplatform: expect/actual declarations, source sets, and exposing shared code to Swift without awkward APIs.
- Build tooling: Gradle Kotlin DSL, version catalogs, convention plugins, KSP versus kapt, and the K2 compiler.
- Testing: JUnit 5 or Kotest, MockK, Turbine for flows and coroutine test dispatchers.
- Server frameworks: Spring Boot or Ktor, dependency injection with Koin or Spring, and database access patterns.
How we vet Kotlin developers
Our recruiters source Kotlin engineers across Latin America. The in-house ARC system ranks the pipeline. Candidates then complete structured NTRVSTA AI interviews tuned to their track: Android, backend or Multiplatform. Recruiters review every candidate before and after the interview and put together a curated shortlist. AI scores are advisory. People decide.
Sample interview topics
- A coroutine launched in a service keeps running after the request that started it is cancelled. Explain why, and how structured concurrency should prevent it.
- When would you use a StateFlow, a SharedFlow and a Channel? Describe a bug you have seen from picking the wrong one.
- You are sharing a repository layer between Android and iOS with Kotlin Multiplatform. How do you design the API so Swift callers get a clean interface for suspend functions and flows?
- A team wants to move a large Java codebase to Kotlin. How do you sequence it, and what interop problems do you watch for?
- Your build uses kapt with several annotation processors and is slow. What would you change, and what risks come with moving to KSP?
Ways to hire Kotlin developers
| Option | Best for | Trade-offs |
|---|
| Freelance marketplace | A short Android task or a proof of concept. | Many profiles list Kotlin but write Java-style code. Deep coroutine skill is hard to confirm. |
| Staffing or recruiting agency | Filling a defined Kotlin role quickly. | Agencies may not separate Android, backend and Multiplatform skills well. |
| In-house recruiting | Long-term hires who will shape your platform. | Slow. Senior Kotlin backend and Multiplatform experience is scarce in many local markets. |
| Ryz Labs staff augmentation | Adding senior Kotlin engineers to your mobile or backend team on US hours. | Custom quote, scoped per team. Built for ongoing work, not hourly gigs. |
| Ryz Labs dedicated team | A Multiplatform or service rebuild needing several engineers and a tech lead. | Requires scoping up front. Best for multi-month programs. |
Ryz is not the right choice if you need engineers on your own payroll as employees with benefits (an employer-of-record partner handles that), or if you want published, self-serve pricing before any conversation.
Why hire Kotlin developers from Latin America
Latin America has a long tradition of Java engineering in financial services, telecom and e-commerce, and many of those teams moved to Kotlin early. That means you can find senior engineers who understand both the JVM's history and modern Kotlin idioms, which is exactly what a Java-to-Kotlin migration needs.
Working within an hour of US time zones, they can pair with your Android or backend leads, join architecture reviews live and respond to production issues during your business day. Our engineers write clear English in pull requests and design docs, which matters for teams that rely on async review.
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FAQ
Do you place Kotlin developers for backend work, or only Android?
Both. We vet Kotlin engineers by track. Some focus on Android, some on Spring Boot or Ktor services, and some on Kotlin Multiplatform. Tell us which you need and we match accordingly.
Is Kotlin Multiplatform ready for production?
Kotlin Multiplatform is stable and used in production for sharing business logic across Android and iOS. Shared UI with Compose Multiplatform is newer on iOS. Our engineers can help you decide how much to share.
What will it cost?
Pricing is a custom quote, scoped per team. You get a plan, a price and the names of the engineers before you sign.
What is the contracting setup, and will they match our hours?
You sign one contract with Ryz. Our engineers work with us as independent contractors, and we handle paying them. They work within ±1h of US time zones, so your standups and reviews happen live.
Can a Kotlin developer join our existing Java team?
Yes. Kotlin runs alongside Java on the JVM, and our engineers are fluent in both. Many teams start by writing new code in Kotlin while keeping existing Java modules as they are.
Questions we didn't answer? Email info@ryzlabs.com.