Which tool or platform do you think is most suitable for developing a new microservice?

The most suitable tool for developing a new microservice in Java is Spring Boot. This framework allows for quick creation of standalone, ready-to-run applications with minimal configuration. Spring Boot supports an embedded server, database integration, security system, and many other components, which facilitates microservice development.

Example of a simple microservice in Spring Boot:

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

@RestController
public class HelloController {
    @GetMapping("/hello")
    public String sayHello() {
        return "Hello from microservice!";
    }
}

Besides Spring Boot, you can consider Micronaut or Quarkus, which are also oriented towards microservice architecture and provide fast startup and low resource consumption.