Javalin vs Ktor: What are the differences?

1. Routing and handling: Javalin provides a straightforward routing API where routes can be defined using lambda functions, making it easy to handle HTTP requests and define custom endpoints. On the other hand, Ktor uses a more declarative approach with a DSL (Domain Specific Language) for routing and handling requests, allowing for greater flexibility in defining routes and handling different types of requests.

2. Scalability: Javalin is lightweight and optimized for small to medium-sized projects, making it a good choice for building microservices or simple web applications. Ktor, on the other hand, is built on an asynchronous programming model, making it well-suited for high-traffic and scalable applications that need to handle many concurrent requests.

3. Framework complexity: Javalin aims to be minimalistic and easy to use, providing only the essential features required for building web applications. Ktor, on the other hand, provides a more feature-rich framework with built-in support for features like authentication, sessions, and server-sent events, making it a better choice for complex enterprise applications that need these additional features out of the box.

4. Coroutines vs Threads: Javalin uses traditional threads for handling concurrency, which can have limitations in terms of scalability and resource usage. Ktor, on the other hand, uses coroutines, which are lightweight and more efficient, allowing for better concurrency and resource utilization.

5. Integration with other libraries: Javalin has better integration with third-party libraries and frameworks, as it has been around for longer and has a larger community. Ktor, on the other hand, has been developed by JetBrains, the creators of Kotlin, and provides seamless integration with other JetBrains tools, making it a good choice for Kotlin developers who already use JetBrains tools like IntelliJ IDEA.

6. Framework popularity: Javalin has been around since 2017 and has gained popularity among Java developers due to its simplicity and ease of use. Ktor, on the other hand, is a relatively newer framework but has been steadily gaining popularity with Kotlin developers, especially those who prefer a more modern and asynchronous programming model.

In Summary, Javalin and Ktor differ in their routing and handling approach, scalability, framework complexity, concurrency model, integration with other libraries, and popularity among developers.