Skip to content

Why the Financial Industry Loves Kotlin

The Kotlin programming language is used widely across various industries. Its features make it particularly well-suited for building financial technology applications. And the financial industry is taking note of that fact.

Industry giants like American Express, Square, and Capital One rely on Kotlin. So do J.P. Morgan and Goldman Sachs. So what is it about Kotlin that makes it so well-suited for the needs of financial institutions?

Kotlin for FinTech

The same features and characteristics that make Kotlin a popular choice for various applications have attracted financial institutions to the language. Specific attributes of Kotlin making it beneficial for fintech development are:

  • Safety: Kotlin's type system and features like null safety help prevent common programming errors that could lead to severe financial consequences.
  • Expressiveness: Kotlin's type inference and higher-order functions make it effortless for developers to express complex financial algorithms and business logic that are both easy to read and maintain.
  • Conciseness: It's easier to write and maintain complex financial applications in Kotlin because its concise syntax helps avoid and eliminate the need for problematic boilerplate code.
  • Interoperability: The finance industry widely adopted Java because of its security, scalability, and stability. So many financial institutions have legacy systems built using Java, which aren’t easy or cheap to replace. It’s more common for these to be updated, modernized, and integrated with new systems. Kotlin easily integrates with existing Java code, making it a good choice for fintech organizations with legacy Java codebases.

Digital financial services company 11:FS uses Kotlin as its programming language. Jason Chow, the company’s lead Kotlin engineer, explains:

“For all its merits, Java is overcomplicated and too boilerplate. That means we’re keeping and maintaining low-value code in our repository. Kotlin was designed to be concise and clear.”

He highlights Kotlin’s concise source code, which makes it easier for financial institutions to maintain, helps reduce time-to-market, and ultimately enables engineers to “focus on high-value problems like customer experience.”

Check out this video to hear why engineers from Xebia’s functional division think Kotlin is a great fit for fintech.

Kotlin is on the rise

Kotlin's popularity has continuously increased in recent years. Its adoption by Google in 2019 as its preferred language for writing Android apps has helped fuel the adoption of Kotlin. Recent comments from Google’s product manager for Kotlin, James Ward, demonstrate that the company is still all-in on Kotlin. He stated: 

“We know that developers are generally more satisfied with Kotlin than with Java. We know that they’re more productive, the quality of applications is higher and so getting more of those people to move more of their code over has been a focus for us. The interoperability of Kotlin […] with Java has made it that people can kind of progressively move code bases over and it would be great to get to the point down the road, where just everything is all Kotlin.”

Surveys like the 2021 JetBrains Developer Ecosystem Survey and others identify Kotlin as one of the fastest-growing programming languages. Other recent surveys and studies demonstrate that Kotlin has become a popular choice among developers for various use cases, including Android development, backend development, and microservices.

As Kotlin continues to gain popularity as a modern and powerful programming language, financial institutions are endeavoring to incorporate its benefits into their ecosystems. Because of this, major banks and others in the finance sector are scrambling to hire Kotlin engineers. And this rise in demand for Kotlin engineers has developers pursuing Kotlin training to meet current needs.


Overall, Kotlin's combination of safety, expressiveness, conciseness, and interoperability make it an excellent solution for building fintech applications.

If you’re interested in learning about migrating your legacy core applications to Kotlin, reach out to us. Xebia’s functional programming experts are seasoned professionals and leaders in the Kotlin community who love helping businesses reap the benefits provided by Kotlin.

Explore more articles