Kotlin Displaces Java: Why Major Companies Are Switching to It in 2025

Kotlin 2025: how the language from JetBrains is taking over the corporate sector

2025 has become a turning point for the JVM ecosystem. The largest tech giants — Google, Uber, Netflix, and Slack — have announced a full or partial transition to Kotlin. If just a few years ago this language was perceived as an "alternative to Java for Android," it has now become the standard for corporate backend development and data engineering.

According to a JetBrains survey (Q1 2025), 68% of large companies with a staff of over 1000 developers already use Kotlin in production, and 22% are in the active migration stage. What is behind this trend?

Why are companies moving away from Java?

• Null safety by default. Kotlin eliminates Java's biggest headache — NullPointerException. The built-in type system allows catching errors at the compilation stage, which is critical for financial and medical systems.
• 100% compatibility. Kotlin compiles to JVM bytecode and works seamlessly with existing Java libraries (Spring, Hibernate, Kafka). This allows for gradual migration without rewriting millions of lines of code.
• Conciseness. Kotlin requires on average 40% less code than Java. For corporate projects with hundreds of thousands of lines, this means reduced code review time and lower maintenance costs.
• Multiplatform. Kotlin Multiplatform (KMP) allows writing shared code for backend (JVM), iOS, Android, and the web. Uber, for example, uses KMP for unified data validation logic across all platforms.

Use cases in 2025: who is transitioning and how

Google is not just a developer of Kotlin, but also its main promoter. In 2025, the corporation announced that all new internal services (including tools for Google Cloud and BigQuery) are written exclusively in Kotlin. Old Java microservices are gradually being "wrapped" in Kotlin modules.

Slack rewrote its core notification engine from Java to Kotlin. Result: a 30% reduction in memory consumption and a 25% acceleration in message processing. Developers noted that Coroutines (Kotlin's lightweight threads) allowed them to abandon complex manual thread pool configuration.

Netflix uses Kotlin for A/B testing of recommendation algorithms. Thanks to type-safe builders and DSL, the data engineering team halved the time needed to write data processing pipelines.

What does this mean for developers?

The job market reacts instantly. According to LinkedIn, demand for Kotlin developers in 2025 grew by 215% compared to 2023. The average salary for a Kotlin engineer in the USA exceeded $160,000 per year, surpassing the figures for Java specialists by 12%.

For beginners, Kotlin has become a "first-wave language": many companies (including Y Combinator startups) now allow writing test assignments in Kotlin instead of Java. At the same time, knowledge of Java remains a plus — Kotlin is tightly integrated with its ecosystem.

And what about Python?

Although Kotlin does not directly compete with Python in ML and AI, it is actively displacing Java in the enterprise segment, where Python once reigned? For backend microservices, high-load systems, and Android — yes. If you work with Java and want to stay in demand in 2025-2026, add Kotlin to your stack — it's not a matter of choice, but a matter of competition.