20+ Kotlin Experts - Available Now

Hire Kotlin Developers

Get dedicated Kotlin developers to build modern Android apps and robust backend services — from Jetpack Compose UIs to Kotlin-powered server-side systems.

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Why choose us?

A boutique shop, not a marketplace.

Pre-vetted engineers only

Every developer passes a 5-stage vetting process.

Dedicated to your project

Your developer works exclusively on your product.

Transparent billing

Hourly time tracking with daily reports. No hidden fees.

Instant replacement

We replace within 48 hours at no extra cost.

Your timezone, your tools

Developers overlap 4-8 hours with your working day.

Scale up or down anytime

Flexible contracts with no lock-in and no penalties.

The exact skill fit for your build.

Kotlin is a modern, statically typed language that has become Google's preferred language for Android development, while also gaining traction as a backend language through frameworks like Ktor and Spring Boot. Its concise syntax, null safety, and full interoperability with existing Java code make it a practical upgrade path for teams already invested in the JVM ecosystem.

At ZonSource, our Kotlin developers have hands-on experience building native Android apps with Jetpack Compose, Kotlin Multiplatform projects that share code across Android and iOS, and backend services using Ktor and Spring Boot. They work confidently with Coroutines for asynchronous programming, Room and SQLDelight for local data, and Retrofit for API integration. Whether you need a new Android app built from scratch, a Java codebase migrated to Kotlin, or a developer to join your existing sprint cycle, our team ships clean, null-safe, well-tested code from day one.

ZS
Kotlin Developer
Senior · 5+ years avg.
KotlinJetpack ComposeCoroutinesKotlin MultiplatformKtorSpring BootRoomRetrofitAndroid SDK
Current Stack
KotlinKotlin
Jetpack ComposeJetpack Compose
Android SDKAndroid SDK
KtorKtor
Spring BootSpring Boot

Skills to look for when hiring.

Every Kotlin developer on our bench is evaluated against these core competencies.

Kotlin Language Fundamentals

Strong grasp of null safety, data classes, extension functions, and idiomatic Kotlin

Coroutines & Asynchronous Programming

Deep understanding of suspend functions, structured concurrency, and Flow

Jetpack Compose

Practical experience building declarative, modern Android UIs

Android Architecture Components

Skilled with ViewModel, LiveData/StateFlow, and Room for local persistence

Kotlin Multiplatform (KMP)

Ability to share business logic between Android and iOS codebases

Backend Development (Ktor/Spring Boot)

Experience building REST APIs in Kotlin on the server side

Dependency Injection (Hilt/Koin)

Comfortable structuring apps with proper DI for testability

Testing (JUnit, MockK, Espresso)

Comfortable writing unit tests and UI tests for reliable releases

Meet the bench.

A snapshot of Kotlin developers available now.

AV
Aditya Verma
Senior Kotlin/Android Developer
8 experience
KotlinJetpack ComposeCoroutinesRoom
Shipped 15+ apps to the Play Store using modern Android architecture
NK
Neha Kulkarni
Kotlin Backend Developer
6 experience
KotlinKtorSpring BootPostgreSQL
Specializes in building REST APIs entirely in Kotlin
RM
Rohan Mistry
Kotlin Multiplatform Developer
5 experience
Kotlin MultiplatformCompose MultiplatformSwift interop
Builds shared business logic across Android and iOS apps
Get a Shortlist Matched to Your Project

The full Kotlin lifecycle.

Everything your project needs, from first line of code to production deployment and beyond.

Custom Android App Development

Build native Android apps using Kotlin and modern Jetpack Compose UI

Kotlin Multiplatform Development

Share business logic across Android and iOS from a single Kotlin codebase

Kotlin Backend Development

Build REST APIs and server-side services using Ktor or Spring Boot

Java to Kotlin Migration

Migrate legacy Java Android or backend codebases to modern, null-safe Kotlin

Kotlin API & Backend Integration

Connect Android apps to REST, GraphQL, and third-party services

Kotlin App Performance Optimization

Improve app startup time, memory usage, and UI rendering performance

Kotlin Testing & Quality Assurance

Set up unit and UI testing with JUnit, MockK, and Espresso

Kotlin App Maintenance & Support

Ongoing bug fixes, OS compatibility updates, and feature development

Simple, transparent pricing.

Share your requirements and we will put together a plan that gives you the best value.

Share Your Requirements · Get a Custom Quote

What clients say about the bench.

OB
Owen Bradley
Founder - FitPulse
★★★★★

ZonSource's Kotlin team rebuilt our Android app with Jetpack Compose and our crash rate dropped to nearly zero.

PN
Priya Nambiar
CTO - PayEase
★★★★★

Their Kotlin backend developer built our payment API and it has run flawlessly in production.

ML
Marcus Lindgren
Head of Mobile - TransitGo
★★★★★

The Kotlin Multiplatform work let us share logic between our Android and iOS apps and cut our dev time significantly.

Requirement to first commit, in under a week.

1

Share Requirements

Tell us your tech stack, project scope, and team needs

Day 1
2

Developer Shortlist

We match you with 2-3 pre-vetted Kotlin developers

Day 2
3

Interview & Select

Interview shortlisted developers, assess skills and culture fit

Day 3-4
4

Onboard & Start

Developer joins your standups, tools, and workflows

Day 5

When to Hire a Kotlin Developer vs a Java Developer

If you're building a new Android app, want to share code with iOS through Kotlin Multiplatform, or simply want more concise, null-safe code, a dedicated Kotlin developer is the right fit. Google has designated Kotlin as its preferred language for Android development, and most new Android tooling and documentation is Kotlin-first.

A Java developer makes more sense if you're maintaining a large, existing Java codebase without immediate plans to modernize, or if your backend team is deeply invested in Java-specific enterprise tooling. Since Kotlin is fully interoperable with Java, many teams migrate incrementally rather than choosing one exclusively.

Kotlin developer interview questions.

Use these questions when evaluating Kotlin developers — or let us handle the vetting.

Q1. What is null safety in Kotlin, and how does it prevent runtime errors?

What to look for

Tests fundamentals — should explain nullable types and safe call operators

Q2. How do Kotlin Coroutines differ from traditional threading?

What to look for

Should describe suspend functions, structured concurrency, and lightweight nature

Q3. What is the difference between LiveData and StateFlow?

What to look for

Tests Android architecture depth — should compare lifecycle awareness and use cases

Q4. How does Jetpack Compose differ from the traditional View-based UI system?

What to look for

Should explain declarative UI and recomposition

Q5. What is Kotlin Multiplatform, and what are its current limitations?

What to look for

Tests currency of knowledge — should give an honest, practical assessment

Q6. How would you approach migrating a Java Android app to Kotlin?

What to look for

Look for an incremental, file-by-file migration plan rather than a risky full rewrite

Q7. How do you handle dependency injection in a Kotlin Android app?

What to look for

Should mention Hilt or Koin and explain the testability benefits

Before you hire.

What skills should a Kotlin developer have in 2026?
Must-haves include core Kotlin fundamentals, Coroutines for async work, and Jetpack Compose for Android UI. Strong additions include Kotlin Multiplatform, Ktor or Spring Boot for backend work, and dependency injection with Hilt or Koin.
How long does it take to onboard a Kotlin developer?
Most ZonSource Kotlin developers can be onboarded and start contributing within 48 hours of finalizing requirements.
Should we use Kotlin or Java for a new Android app?
Kotlin is Google's officially preferred language for Android development, with more concise syntax, built-in null safety, and first-class support in modern Android tooling like Jetpack Compose.
Can Kotlin be used for backend development, not just Android?
Yes, Kotlin works well for backend services using frameworks like Ktor or Spring Boot, and many teams use it on both the app and server side for a more unified codebase.
Can you migrate our Java codebase to Kotlin?
Yes, our team handles incremental Java to Kotlin migrations, since Kotlin's full Java interoperability allows both languages to coexist safely during the transition.
Do you offer a trial period before hiring a Kotlin developer full-time?
Yes, we offer a 2-day risk-free trial so you can evaluate the developer's skills before committing long-term.
Will the Kotlin developer work in our timezone?
Our developers offer 4-6 hours of daily overlap with US timezones and full overlap with European and APAC teams.

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