How to hire Kotlin developers: an executive guide

Your app roadmap is set, your backend needs to scale, and the Kotlin developer position has been open for weeks. Resumes keep coming in, but few candidates hold up in the technical interview. If this sounds familiar, you are not alone: hiring Kotlin developers has become a strategic challenge for companies of every size.

The reason is simple. Kotlin is no longer a bet; it is the market standard. According to Google, 95% of the top 1,000 apps on Google Play contain Kotlin code. Demand has grown faster than the supply of experienced professionals, and a wrong hire is expensive.

In this guide, you will learn which Kotlin developer profiles exist, which skills to evaluate, how much it costs to hire, which hiring models fit each scenario and how to avoid the most common mistakes.

Quick summary

• What it is: Kotlin is Google’s preferred language for Android and is also used for backend development (Spring Boot, Ktor) and multiplatform projects.
• How much it costs: the average base salary for a Kotlin developer in the US is about US$ 117,000 per year, before benefits and taxes; nearshore talent from Latin America offers significant savings.
• How long it takes: a traditional hiring process usually takes 6 to 10 weeks, plus 1 to 4 weeks of onboarding.
• Which model to choose: in-house hiring for core long-term roles; staff augmentation to gain speed, flexibility and reduce risk.

If you need someone shipping Kotlin code in the next few weeks, the fastest path may not be opening a position, but adding validated specialists to your team. That is exactly what NextAge’s Staff Augmentation does, and we explain the model in detail later in this guide.

Why hire Kotlin developers?

Kotlin is a modern language created by JetBrains that runs on the JVM and is fully interoperable with Java. Since 2019, Android has officially been Kotlin-first, meaning Google prioritizes Kotlin in its tools, libraries and documentation. For businesses, this translates into more stable apps, less code to maintain and faster delivery.

Business benefits, not just technical ones

Choosing Kotlin has a direct impact on the metrics that matter to leadership:

• Fewer production failures: among the top 1,000 apps on Google Play, those using Kotlin have 20% fewer crashes per user. Kotlin’s null safety prevents NullPointerExceptions, the leading cause of crashes on Android.
• Higher productivity: 67% of professional developers who use Kotlin say it has increased their productivity.
• Less code to maintain: after moving new feature development to Kotlin, the Google Home team reduced its codebase size by 33% and NullPointerException crashes by 30%.

It is no coincidence that more than 70 of Google’s own apps, such as Maps, Drive and Play, are built with Kotlin. Companies like Netflix, Uber, Duolingo, N26 and AWS also run Kotlin in production, according to the State of Kotlin 2026 report.

Kotlin goes far beyond Android

Many leaders still associate Kotlin only with Android apps. In practice, the language has gained ground on other fronts:

• Backend: JetBrains and Spring formalized a strategic partnership, and 27% of Spring developers have already used Kotlin. Spring Boot 4 now uses Kotlin 2.2 as its baseline.
• Multiplatform: with Kotlin Multiplatform (KMP), teams can share business logic across Android, iOS, web and backend. Compose Multiplatform for iOS reached stable status in 2025, and Google already uses KMP in production in the Google Docs iOS app.

Kotlin vs. Java: the key differences

For companies with a Java legacy, this compatibility is decisive: migration can happen gradually, module by module, without rewriting the entire system.

What kind of Kotlin developer does your company need?

Before opening a position, define the profile. An Android developer and a backend Kotlin developer have different routines, tools and skills; hiring the wrong profile is one of the most common causes of frustration in the first months.

If your goal is to build an app from scratch, rather than just strengthen your internal team, NextAge can also take the project end to end with its Web and Mobile Development service.

Junior, mid-level or senior: when each makes sense

• Junior: suited for teams with strong technical leadership and well-defined tasks. Requires close guidance.
• Mid-level: delivers features independently within an established architecture. The most sought-after profile for strengthening squads.
• Senior: essential for architecture decisions, Java to Kotlin migrations, performance issues or when the professional will be the technical reference for the team.

Essential skills of a Kotlin developer

A strong Kotlin developer goes beyond syntax: they use the language’s features to write code that is safe, testable and easy to maintain. Here is what to evaluate.

Hard skills

• Null safety and the type system: deliberate use of nullable types, sealed classes and smart casts.
• Coroutines and Flow: mastery of structured concurrency, cancellation and error handling in asynchronous operations.
• Java interoperability: ability to work in mixed codebases and lead gradual migrations.
• Profile-specific frameworks: Jetpack Compose for Android; Spring Boot or Ktor for backend; KMP for multiplatform.
• Automated testing: JUnit 5, MockK, Kotest and Turbine for testing asynchronous flows.
• Architecture: MVVM, MVI and Clean Architecture on mobile; hexagonal architecture and DDD on the backend.
• Current tooling: Gradle Kotlin DSL, KSP and the K2 compiler, which according to JetBrains cut compilation time by more than 40% in large projects.

Soft skills

Clear communication with business stakeholders, autonomy to solve problems, product mindset and solid written English for documentation and async work. In distributed teams, the ability to communicate asynchronously is as important as the code itself.

Red flags during evaluation

• Overuse of the !! operator, which defeats the language’s main safety net.
• Difficulty explaining why a particular architecture was chosen.
• No experience debugging coroutines in production.
• Java-style code written in Kotlin, without taking advantage of the language’s features.

Junior vs. senior in practice

How to hire a Kotlin developer: step by step

Hiring well requires a process. These eight steps reduce the risk of a bad hire:

1. Define the scope and profile: Android, backend or multiplatform, plus the required seniority level.
2. Choose the hiring model: in-house, freelancer, agency or staff augmentation (we compare them below).
3. Write a specific job description: include the stack, real project challenges and the salary range. Generic postings attract generic candidates.
4. Source from the right channels: LinkedIn, GitHub, Kotlin and Android communities, the official Kotlin Slack community (with more than 100,000 members) and specialized staff augmentation partners.
5. Run an objective technical screening: prefer reviewing a real pull request or a short challenge tied to your product over generic algorithm exercises.
6. Conduct the technical interview with real scenarios: ask the candidate to walk you through a system they built, how they handled errors and what they would do differently today.
7. Assess communication and cultural fit: the developer needs to work well with product, design and business teams.
8. Plan the onboarding: access, documentation and a tech lead or mentor as a reference for the first weeks.

Eight steps, 6 to 10 weeks and no guarantee of success. At NextAge, the best Kotlin specialists on the market have already gone through this screening: every professional is validated in internal projects before joining your team, with a dedicated tech lead and a 15-day risk-free period. Discover NextAge’s Staff Augmentation.

How much does it cost to hire a Kotlin developer?

In the United States, the average base salary for a Kotlin developer is about US$ 117,300 per year, with typical pay ranging from US$ 94,225 to US$ 147,451, according to Glassdoor data cited by Lemon.io. Senior roles can exceed US$ 160,000. Once benefits, payroll taxes and equipment are added, the fully loaded cost of an in-house hire is 30% to 50% higher.

Source: Lemon.io. Rates vary by seniority, specialization and location.

The costs that don’t show up on the salary line

When calculating the investment, also consider indirect costs:

• Benefits and taxes: health insurance, paid time off, retirement contributions and payroll taxes significantly raise the monthly cost of an in-house hire.
• Time-to-hire: a traditional process takes 6 to 10 weeks, plus 1 to 4 weeks of onboarding. During that time, your roadmap stands still.
• The cost of a bad hire: according to Lemon.io, a wrong hire can cause 6 to 8 weeks of delay and US$ 20,000 to 40,000 in rework, plus the technical debt left in the codebase.
• Turnover: experienced Kotlin developers receive offers frequently; retaining talent also has a cost.

And once your app is live, the nature of the cost changes: maintaining, fixing and evolving the system requires a different approach. For this stage, NextAge offers Software Management Services.

In-house, freelancer, agency or staff augmentation: which model to choose?

There is no single right model for every case; there is the right model for your company’s current moment. The table below summarizes the main differences:

A practical rule for deciding:

• Core long-term product with an established internal team: in-house hiring makes sense for strategic roles.
• One-off, well-defined task: a freelancer can work, as long as you have the technical capacity to vet and oversee them.
• Tight deadlines, need to scale fast or a complete squad: staff augmentation with validated professionals is the safest path.

What is NextAge’s Staff Augmentation, and how is it different from a body shop?

NextAge’s Staff Augmentation is an exclusive methodology for adding developers and complete squads to your company without the problems of traditional outsourcing. In the body shop model, the client receives a resume, takes on management of the professional and bears the risk if the placement does not work out. NextAge’s Staff Augmentation works differently:

• Validated specialists: every Kotlin developer is evaluated in internal projects before being assigned to a client.
• Management handled by NextAge: each team has a dedicated tech lead, so your company can focus on what is strategic.
• 15 days risk-free: if what was promised is not delivered, cancellation is penalty-free.
• Flexible contract: easily expand or reduce the team according to your needs.
• Higher productivity: the methodology enables teams to achieve up to 40% more productivity compared to other companies, at no additional cost.
• Nearshore advantage: top-tier talent from Brazil, with substantial time-zone overlap with North America and competitive rates.
• Proven track record: more than 19 years in the market, over 600 projects, presence in more than 13 countries and clients such as Sicredi, XP, WEG, Scania and Benner.

NextAge’s Kotlin specialists work on Android, backend with Spring Boot and Ktor, and multiplatform projects, and can join as individual professionals or as a complete squad with QA, UX/UI and Scrum Master. Learn more about NextAge’s Staff Augmentation.

“The partnership with NextAge in Staff Augmentation was essential to accelerate our development and innovation projects.” (Benner, company with the leading management software in the Brazilian market)

Checklist for hiring the right Kotlin developer

Use this list before closing any hire:

• The profile (Android, backend or multiplatform) and seniority are defined.
• The hiring model was chosen based on total cost, timeline and risk.
• The job description includes the stack, real challenges and salary range.
• The technical test is tied to your product, not generic exercises.
• The candidate demonstrated command of coroutines and null safety.
• There is proven experience with automated testing.
• The developer can work with legacy Java code, if that applies to you.
• Communication was assessed with product or business stakeholders.
• The onboarding plan is ready, with access, documentation and a mentor.
• Goals for the first 30 days are defined and agreed upon.

Frequently asked questions about hiring Kotlin developers

How much does it cost to hire a Kotlin developer?

In the US, the average base salary for a Kotlin developer is about US$ 117,000 per year, and the fully loaded cost can be 30% to 50% higher, according to Lemon.io. Experienced nearshore developers from Latin America typically cost US$ 40 to 80 per hour.

Where can I find qualified Kotlin developers?

The main channels are LinkedIn, GitHub, Kotlin and Android communities, tech events and staff augmentation partners. Specialized companies such as NextAge shorten the search because their professionals are already vetted.

Is Kotlin only for Android?

No. Kotlin is the preferred language for Android, but it is also widely used on the backend, with Spring Boot and Ktor, and in multiplatform projects with Kotlin Multiplatform, which allows sharing code across Android, iOS and web.

Should I hire in-house, use freelancers or choose staff augmentation?

It depends on the context. In-house hiring is best for strategic long-term roles. Freelancers work for one-off tasks if you can vet them yourself. Staff augmentation is the best option when you need speed, flexibility to scale and lower hiring risk.

How long does it take to hire a Kotlin developer?

A traditional hiring process takes, on average, 6 to 10 weeks, plus 1 to 4 weeks of onboarding. With staff augmentation and pre-validated professionals, this timeline drops to a few weeks.

What skills should a senior Kotlin developer have?

Command of coroutines and structured concurrency, null safety, Java interoperability, automated testing and the ability to make and justify architecture decisions. A senior developer should also mentor the team and communicate well with business stakeholders.

Can a Java developer switch to Kotlin quickly?

Yes, the initial learning curve is short, because both languages run on the JVM and are fully interoperable. However, mastering features such as coroutines and idiomatic functional programming takes practice, so for critical projects it is worth prioritizing developers with production Kotlin experience.

What is Kotlin staff augmentation?

It is the practice of adding Kotlin professionals to your team through a specialized company that handles selection, contracts and, in models like NextAge’s Staff Augmentation, also the technical management of the team. Your company gains agility without the bureaucracy of direct hiring.

Conclusion: the right developer makes a difference in results

Hiring Kotlin developers requires three well-made decisions: defining the right profile for the project, evaluating skills in practice and choosing the hiring model that balances cost, timeline and risk. When these steps are done carefully, Kotlin delivers on its promise: more stable apps, cleaner code and more productive teams.

Want the best Kotlin specialists on your project, without months of recruiting? Talk to NextAge and get a free assessment of your IT operation, with a personalized plan to build your Kotlin team.

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