Kotlin developers
Rates, hiring difficulty, a hiring guide and interview questions for a Kotlin developer: everything in one place.
Overview
Kotlin developers build Android applications, backend services (Ktor, Spring Boot), and increasingly cross-platform mobile apps with Kotlin Multiplatform (KMP). Kotlin's concise syntax, null safety, and coroutines make it a productive alternative to Java across the JVM ecosystem.
Hiring Kotlin developers is competitive. The talent pool is large but so is demand, so senior people get snapped up quickly.
Retention: 47% of developers who use Kotlin want to keep using it, and 6% of those who do not use it yet want to start.
Open roles per 1,000 developers Full ranking →
US job postings (30 days) divided by developers who use each stack. Higher means harder to hire.
What a Kotlin developer costs
Contract and salary benchmarks for the US.
Contract rate
C2C or 1099, from W-2 hourly × 1.3–1.6 for tax, benefits and overhead.
W-2 equivalent
BLS median for US software developers ($135,980), adjusted +11% for Kotlin using Stack Overflow 2025 pay data (359 respondents).
Full-time contractor cost
Per year at 40 hours a week.
Agencies typically bill 2–3× W-2 pay. See what a full project costs, compare W-2, 1099 and C2C, or check rates by state.
How to hire a Kotlin developer
What good looks like, and what should worry you.
Typical projects
- Native Android applications with Jetpack Compose
- Backend services with Ktor or Spring Boot + Kotlin
- Kotlin Multiplatform Mobile (KMM) shared business logic
- Migration from Java to Kotlin in existing codebases
- Gradle build system customization and plugins
Team setup
Kotlin developers often come from Java backgrounds, which is fine as long as they've genuinely adopted Kotlin idioms. For Android projects, Kotlin is mandatory — there's no reason to write new Android code in Java. For backend work, Kotlin + Spring Boot is a safe enterprise choice, while Ktor is lighter for microservices. If you're building for both Android and iOS, Kotlin Multiplatform lets you share business logic while keeping native UIs, and Kotlin developers are the natural choice to lead that effort.
What to look for
- Idiomatic Kotlin: extension functions, sealed classes, data classes, scope functions (let, apply, run)
- Coroutines and Flow for async programming — not just wrapping callbacks
- Null safety discipline: uses the type system properly instead of !! everywhere
- Platform-specific experience: Android (Compose, Jetpack) or backend (Ktor, Spring Boot)
- Kotlin Multiplatform experience if you need cross-platform code sharing
Red flags
- Writes Kotlin like Java — getters/setters, nullable types everywhere, no use of Kotlin idioms
- Uses !! (not-null assertion) liberally — defeats Kotlin's null safety
- Can't explain coroutine scopes and structured concurrency
- No experience with the specific platform you're hiring for (Android vs backend)
- Doesn't understand Kotlin's interop with Java — important for mixed codebases
Interview questions
Questions that separate strong candidates from people who just list the keyword.
- How does Kotlin's null safety system work? Walk me through how you handle nullable types in practice.
- Explain coroutine scopes. What's the difference between viewModelScope, lifecycleScope, and a custom scope?
- How do you structure a Kotlin Multiplatform project? What goes in shared vs platform-specific code?
- Compare sealed classes and enums in Kotlin. When would you use each?
- How do you handle dependency injection in a Kotlin project? Compare Hilt, Koin, and manual DI.
Hiring trend
How often Kotlin appears in startup hiring posts over time.
Hacker News “Who’s Hiring” posts mentioning Kotlin, by year (2015–Feb 2025). Peak: 2018 with 108 posts. HN hiring overall has fallen since 2019, so compare stacks rather than reading absolute numbers. Its share of current US job postings changed -18% since April 2026.
Similar stacks
Related skills, with their rates and hiring difficulty.
Need Kotlin developers?
We take on contract Kotlin work, from one developer joining your team to building the whole product. Tell us what you need and we'll reply by email.
- MVPs and new products
- Developers for your existing team
- Rescuing stalled projects
- AI features
Questions
How much does a Kotlin developer cost?
Contract Kotlin developers typically bill $94–116/hr (C2C or 1099). The W-2 equivalent salary is about $150,900. Agencies usually charge 2–3× W-2 pay.
Is it hard to hire Kotlin developers?
Kotlin is rated High on our hiring difficulty index (53/100, #19 of 29), with about 12 open US roles for every 1,000 developers who use it.
Should I hire a full-time Kotlin developer or use a contractor?
If the work is ongoing and core to your product, hire. If you need to start quickly, cover a gap, or the role is hard to fill, a contractor or agency gets work moving while you search.