Is Tomcat Still King? 5 Reasons Devs Switch in 2025

Long Live the King? Tomcat's Legacy in a Modern World

For decades, Apache Tomcat has been the undisputed monarch of the Java web server world. It's stable, reliable, and has powered countless enterprise applications. If you've been a Java developer for any length of time, you've almost certainly deployed a WAR file to a Tomcat instance. It's the grizzled, dependable workhorse that just works.

But the technological landscape of 2025 is vastly different from the one where Tomcat first earned its crown. The rise of cloud computing, containers, and microservices has fundamentally changed what developers need from an application server. Speed, efficiency, and a seamless developer experience are now paramount. This has led to a crucial question in development circles: Is Tomcat still king?

While Tomcat is far from obsolete, a growing number of developers are migrating to newer, more agile alternatives for their greenfield projects. Here are five key reasons behind this shift.

Reason 1: The Inexorable Rise of Microservices

The single biggest driver behind the shift away from traditional Tomcat deployments is the architectural pivot to microservices. The old way involved bundling your entire application into a single monolithic WAR file and deploying it to a shared Tomcat server. This server was a heavyweight, long-running process designed for stability over agility.

The Monolith vs. Microservice Mindset

Microservice architectures require a different approach. Each service is a small, independent application that needs to start up quickly, have a minimal footprint, and be easily containerized. Frameworks like Spring Boot (which often embeds a stripped-down Tomcat, Jetty, or Undertow), Quarkus, and Micronaut were built from the ground up for this paradigm. They bundle the server with the application, creating a self-contained, executable JAR. This model offers several advantages:

• Isolation: No more "dependency hell" from multiple applications on a single server.
• Scalability: You can scale individual services based on demand, rather than scaling the entire monolith.
• Rapid Deployment: Lightweight, self-contained artifacts are perfect for CI/CD pipelines and container orchestration platforms like Kubernetes.

Trying to shoehorn a traditional, standalone Tomcat server into a modern, dynamic microservices environment often feels like fitting a square peg in a round hole. The new kids on the block are simply a more natural fit.

Reason 2: Performance & Resource Efficiency in the Cloud

In the cloud, every millisecond of startup time and every megabyte of RAM costs money. This is where modern Java frameworks truly shine and where traditional Tomcat can lag.

The Cost of Containerization

Tomcat was designed in an era of bare-metal servers where startup time was a one-time cost and memory was less of a premium. In a containerized world, especially with serverless functions or auto-scaling groups, applications may be started and stopped frequently. A 30-second startup time is unacceptable when you need to scale in response to a sudden traffic spike.

Modern alternatives are obsessively optimized for:

• Fast Startup: Frameworks like Quarkus and Micronaut perform significant processing at build time, leading to near-instantaneous startup times. This is crucial for serverless functions and rapid scaling.
• Low Memory Footprint: By reducing reflection and performing dependency injection at compile time, these frameworks create leaner runtimes. A smaller memory footprint means you can pack more containers onto a single host, directly reducing your cloud infrastructure bill.

While an embedded Tomcat within Spring Boot is much more efficient than a standalone instance, frameworks designed specifically for cloud-native performance often have a significant edge.

Reason 3: A Revolution in Developer Experience (DevEx)

Today's developers expect tools that boost productivity and get out of the way. The cycle of code -> compile -> build WAR -> deploy to server -> restart -> test feels painfully slow in 2025. Modern frameworks have made this a core focus, offering a vastly superior developer experience.

Convention Over Configuration

This principle, popularized by Spring Boot, has become the standard. Instead of wading through endless XML configuration files to wire up a database or a message queue, developers can often just add a dependency, and the framework handles the rest with sensible defaults. Other key DevEx improvements include:

• Live Reload: Make a change to your code, and the running application updates automatically. Quarkus and Micronaut have taken this to a new level with incredibly fast feedback loops.
• Integrated Tooling: Modern CLI tools help you bootstrap projects, add extensions, and run tests with simple commands.
• Simplified Configuration: Properties files (e.g., `application.properties` or `application.yml`) have replaced complex XML, making configuration easier to read, write, and manage across different environments.

This focus on productivity allows developers to spend more time writing business logic and less time wrestling with boilerplate and server configuration.

Tomcat vs. The Contenders: A 2025 Showdown

Reason 4: The Shift to Reactive and Asynchronous Paradigms

The traditional web server model is thread-per-request. For every incoming connection, a thread is blocked until the request is fully processed. This model is simple but struggles under very high concurrency, as threads are a finite and expensive resource.

The reactive model, in contrast, uses a non-blocking, event-driven approach. A small number of threads (an event loop) can handle thousands of concurrent connections by delegating I/O operations and processing responses as they become available. This is far more resource-efficient for I/O-bound applications like API gateways or services that call other services.

While Tomcat has adapted with its non-blocking I/O connector (Coyote), its fundamental architecture wasn't built around this concept. Frameworks like Spring WebFlux (which runs on Netty by default), Vert.x, and Quarkus (with its use of Netty and Vert.x) have embraced the reactive paradigm from their core, offering a more integrated and performant solution for building highly concurrent applications.

Reason 5: GraalVM and the Quest for Native Performance

Perhaps the most exciting frontier in the Java world is GraalVM Native Image. This technology compiles Java code ahead-of-time (AOT) into a self-contained, platform-specific native executable, much like an application written in Go or Rust.

The benefits are staggering:

• Near-instantaneous startup: We're talking tens of milliseconds, not seconds.
• Drastically reduced memory consumption: The JVM is not required at runtime, slashing memory overhead.
• Smaller container images: The executable is lean and self-contained.

This is a game-changer for serverless computing and any scenario where startup performance is critical. Quarkus and Micronaut were designed from day one with GraalVM in mind. They avoid reflection and dynamic class loading, which are problematic for AOT compilation. Spring has also made great strides with its Native Image support, but the frameworks built for it from the ground up often provide a smoother path.

For standalone Tomcat, achieving a native image is a complex, often impractical endeavor due to its heavy reliance on the dynamic features of the JVM that GraalVM struggles with.

Conclusion: Tomcat's New Role as a Respected Elder Statesman

So, is Tomcat's reign over? The answer is nuanced. Tomcat is not dead, nor is it dying. It remains an excellent, stable, and secure choice for many existing monolithic applications and for environments where its Jakarta EE compliance is a hard requirement. Its role as the default embedded server in many Spring Boot applications also secures its relevance for years to come.

However, for new projects in 2025—especially those targeting cloud-native, microservice, or serverless architectures—the crown has clearly been passed. Developers are switching not because Tomcat is bad, but because frameworks like Quarkus, Micronaut, and Spring Boot are purpose-built for the demands of the modern era. They offer superior performance, a smaller footprint, and a developer experience that allows teams to build and ship faster and more efficiently.

The king isn't dead, but the kingdom has evolved. Tomcat has earned its place as a respected elder statesman, while a new generation of agile, cloud-native rulers takes the throne.