5 Best server-side Kotlin frameworks

5 Best server-side Kotlin frameworks
5 Best server-side Kotlin frameworks

There are numerous frameworks that support server-side development with Kotlin. For offering more concise APIs, spring started to use it, beginning from version 5.0.

Spring comes with an online project generator that allows developers to quickly generate a new project in Kotlin. This created a hike in the server-side development using Kotlin. Many front end-developers took up server-side development, while many pre-existing Java server-side developers switched to Kotlin. It is now backed by numerous server-side frameworks, the top ones are discussed below.

Reasons for choosing Kotlin for Server-side Development:

Kotlin is a perfect pick for developing applications for the server end, as it allows developers to write concisely as well as distinct codes. At the same time, Kotlin maintains thorough compatibility with the pre-existing Java-based technology stacks. The learning curve of Kotlin is very smooth; thereby it is easily accepted by learners.

  • Smooth Learning Curve: Switching to Kotlin or learning Kotlin concurrently with Java is very easy for developers. Initially, you can cheque your code by using the in-built automated Java to Kotlin converter that comes with the Kotlin plugin. Then we have the Kotlin Koans, which serves as a complete guide, it comes with the key features of the language along with several interactive exercises for beginners as well as intermediate programmers.
  • Migration: Kotlin was created with a vision to support conversions from Java. Hence, it allows gradual support that is the step by step migration of large codebases from Java to Kotlin. It even allows you to add new lines of codes in Kotlin while the older subparts of your application are in Java.
  • Interoperability: Kotlin is fully compatible with the entire range of Java-based frameworks. It is even backwards compatible with the lower versions of the Java-based frameworks. It allows you to work with familiar technology stack while availing the benefits of a contemporary language.
  • Tools: Along with the general highly efficient IDE support, Kotlin offers a wide range of framework-specific tools. For instance, to use spring in the project, you can add the plugin for IntelliJ IDEA Ultimate.
  • Scalable: We can create server-side applications that can manage a massive number of clients with a minimal hardware requirement by exploiting Kotlin’s support for coroutines.
  • Expressive: Innovative language features such as support for delegated properties and type-safe builders, allow Kotlin to create efficient and easily accessible abstractions.

Top 5 frameworks for server-side development with Kotlin

Javalin: Javalin is referred to as the most lightweight web framework for Kotlin and Java server-side development. Javalin supports network configuration components such as Web Sockets, HTTP2 and async requests and so on. Javalin can be merely termed as Jetty with a few thousand lines of code.

Javalin was initiated as a fork (clone) of Java; on top of those several elements of the Kotlin web framework Spark were added. Although it was not anticipated by its developers, still Javalin emerged into a wider framework. It was moulded into a ground-up rewrite, with reference to the JavaScript framework koa.js. The framework is updated on a regular basis. Since its first release, almost every month two new versions are released. It is ensured that every minor version is backwards compatible.


  • It is easy to use and implement for beginners.
  • It comes with a few tutorials and manuals. Hence, it is recommended for developers who are switching to backend development initially.
  • Its prime objective is to complete the tasks rapidly.
  • It is embedded on the Jetty server.
  • It is a Real micro-framework.
  • It uses Lambda- based Web Socket API.
  • It is known for being lightweight and fast, especially in contrast to its alternatives.


  • The document is not well-structured. It assumes that the person has prior knowledge about Javalin, a beginner would get completely lost.
  • Javalin doesn’t overlap the standard terminology. As in, what we address as Routes and Filters usually is clubbed as Handlers in it. This makes it difficult to track handler in Javalin when you refer to some tutorials in which Routes and Filters are mentioned.
  • It focuses on completing the tasks rapidly; this can be a disadvantage in some of the projects.
  • It is still under-development. The To-add feature stack is still full, to overcome this shortcoming, you need to seek for and include external dependencies.

KTor: It is a very light framework that reduces the effort required to create web applications in Kotlin. It doesn’t manipulate the underlying technologies of a project and is compatible with most of them, with very rare exceptions. Ktor framework is built by JetBrains for creating Web applications in Kotlin.

It is highly reliable, as it is a product of the Kotlin team, itself. It allows developers to rapidly create both, client and server-side applications that target multiple platforms. Ktor exploits Kotlin Coroutines for providing high scalability and offers an efficient and idiomatic API for developers.


  • It is completely reliable and stable as it comes from the JetBrains.
  • It works on a minimum memory footprint and comes in as a lightweight thread.
  • It is a rapid development framework.
  • Most suitable for prototyping
  • Analogous to Javalin, it is also a real micro-framework.


  • The Ktor is the community is quite small as compared to Javalin.
  • It is new in the industry and needs some time to mature.
  • In order to use it for server-side development, you need to be thorough with the basics as you won’t be able to trace the document.
  • You need to use several third-party libraries for adding complex features, similar to Javalin.

Spark: Spark is one of the earliest expressive Kotlin or Java web framework built for rapid development. It can also be used higher-level Kotlin development. It is not so popular, as till today support in the alpha version. Spark is not so trusted with respect to micro-services.


  • It is swift as well as lightweight.
  • It occupies a minimum memory footprint.
  • Just like its competitors, it is also a real micro-framework.
  • Analogous to Javalin, it is also embedded Jetty server.
  • It is fully compatible with Angular.
  • It is very elementary to setup.
  • Most suitable for rapid prototyping.


  • It is not recommended for large-scale projects.
  • The documentation lacks details; it is not advisable for beginners.

Spring Boot: The Spring Boot framework is widely used for creating stand-alone Spring based Applications. The applications created are of large-scale, production-grade, while you just need to trigger the run button.


  • It has the potential to create stand-alone spring applications.
  • Easy installation and set-up procedure.
  • Comes from the Spring ecosystem.
  • It is a modular framework.
  • It is compatible with a wide range of external libraries.
  • It is designed keeping the enterprise requirements in mind.
  • It has a very dense community of developers including many early Java developers.


  • The document is highly fragmented. As there are multiple sources and versions, with high diversity. Be particular about picking the most suitable one for your project.
  • The documentation is not that elaborate.
  • Abrupt changes between versions. The changes are not smooth, and some of the useful features are missing in the contemporary versions.

Vert.X: Just like Java and Kotlin, Vert.X is an ecosystem used for building reactive applications in different programming languages. Vert.X comes with a powerful set of tools. However, it is not advisable for everyone. It comes with detailed documentation and is thoroughly compatible with Kotlin libraries. It creates reactive Web applications for the Java Virtual Machine.


  • Used for rapid development.
  • Vert.x comes as a complete ecosystem of tools.
  • It is very well modularised.
  • It occupies a smaller memory footprint as compared to Spark.
  • It comes with WebSockets support.
  • It follows the Reactive systems approach.
  • The main objective is to create loosely-coupled, flexible and highly-scalable applications.


  • It is not advised for beginners. Being a reactive toolkit, it belongs to a specific domain, unlike its alternatives.
  • If you are working on Spring Boot framework, it won’t be smooth for you to switch over to Vert.X.

Apart from the above mentioned top-notch frameworks, there are a few more Kotlin Server-side Development frameworks:

  • kotlinx.html: It is a digital subscriber line used for building HTML for Web applications. With its advanced features, it has substituted the traditional templating systems including JSP and FreeMarker.
  • Micronaut: It is a contemporary, JVM-based, full-stack development framework used for building easily testable, modular microservice-based or serverless applications. It comes with a wide range of in-built and handy features.

The server-side frameworks are making a huge impact in the development industry by allowing rapid server development. To read more about Kotlin, click here.

By Vanshika Singolia