Understanding Java Virtual Threads and Their Performance Benefits in SpringBoot

Virtual threads, introduced in Java 19, provide a lightweight threading model similar to Go's goroutines, allowing millions of threads to be created on top of a few OS threads.

The article outlines the key differences between virtual and regular threads, emphasizing that virtual threads consume far less memory and can be scheduled by the JVM rather than the operating system.

To use virtual threads in a SpringBoot application (Java 20, SpringBoot 3.1.2), the author provides a simple configuration class that enables @ConditionalOnProperty to switch between virtual and ordinary thread executors, and replaces the default async task executor and Tomcat protocol handler with Executors.newVirtualThreadPerTaskExecutor():

@Configuration
@ConditionalOnProperty(prefix="spring", name="virtual-thread", havingValue="true")
public class ThreadConfig {
    @Bean
    public AsyncTaskExecutor applicationTaskExecutor() {
        return new TaskExecutorAdapter(Executors.newVirtualThreadPerTaskExecutor());
    }

    @Bean
    public TomcatProtocolHandlerCustomizer<?> protocolHandlerCustomizer() {
        return protocolHandler -> protocolHandler.setExecutor(Executors.newVirtualThreadPerTaskExecutor());
    }
}

An asynchronous service method simulates a 50 ms I/O operation, and a test invokes this method 100 000 times, measuring total execution time. Using ordinary threads the test takes about 678 seconds, while virtual threads finish in roughly 3.9 seconds—a speedup of nearly 200×.

The author also compares HTTP request latency under 500 concurrent threads with a simple endpoint that sleeps 50 ms. Ordinary threads show median and high‑percentile latencies above 150 ms, whereas virtual threads keep the maximum latency under 100 ms, demonstrating better resource utilization.

In conclusion, virtual threads deliver significant performance gains for I/O‑bound workloads such as typical web applications, but offer less benefit for CPU‑bound tasks. The article encourages upgrading from older Java versions to leverage this feature.