Spring Boot Rest Hello World poor performance

Question

My motivation for this question are slow response times of our application's REST endpoints, ca 500ms.

To narrow down the cause, I followed this Spring Boot getting started tutorial and created very basic single endpoint app. And the repsponse times are the same, ca 500ms.

Code:

@RestController
public class Rest {

    @GetMapping("/rest")
    public String index() {
        return "Greetings from Spring Boot!";
    }
}

@SpringBootApplication
public class App extends SpringBootServletInitializer {

    @Override
    protected SpringApplicationBuilder configure(SpringApplicationBuilder application) {
        return application.sources(App.class);
    }

    public static void main(String[] args) {
        SpringApplication.run(App.class, args);
    }
}

pom.xml:

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>com.kousalik</groupId>
    <artifactId>boot</artifactId>
    <version>1.0-SNAPSHOT</version>
    <packaging>war</packaging>
<properties>
    <java.version>1.8</java.version>
    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
</properties>

<parent>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-parent</artifactId>
    <version>1.5.6.RELEASE</version>
</parent>

<dependencies>
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-web</artifactId>
    </dependency>
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-tomcat</artifactId>
        <scope>provided</scope>
    </dependency>
</dependencies>

<build>
    <plugins>
        <plugin>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-maven-plugin</artifactId>
        </plugin>
    </plugins>
</build>

The response times with embedded Tomcat are the same, ca 500ms.

Why is Spring Boot so slow by default? All I found about performance usualy mentions only startup speed, memory fottprints etc. What is wrong with this simple example?

I'm running it on Win 10, JDK 1.8.144, Tomcat 8.5.20.