WebSocket과 STOMP는 언제 실시간 연결에 필요할까요?

GET /notifications HTTP/1.1
Accept: application/json

HTTP/1.1 200 OK
Content-Type: application/json

[
  {
    "id": 1,
    "message": "새 댓글이 달렸어요"
  }
]

{
  "roomId": "spring",
  "message": "안녕하세요"
}

dependencies {
    implementation "org.springframework.boot:spring-boot-starter-websocket"
}

package com.example.realtime;

import org.springframework.context.annotation.Configuration;
import org.springframework.messaging.simp.config.MessageBrokerRegistry;
import org.springframework.web.socket.config.annotation.EnableWebSocketMessageBroker;
import org.springframework.web.socket.config.annotation.StompEndpointRegistry;
import org.springframework.web.socket.config.annotation.WebSocketMessageBrokerConfigurer;

@Configuration
@EnableWebSocketMessageBroker
public class RealtimeWebSocketConfig implements WebSocketMessageBrokerConfigurer {

    @Override
    public void registerStompEndpoints(StompEndpointRegistry registry) {
        registry.addEndpoint("/ws")
                .withSockJS();
    }

    @Override
    public void configureMessageBroker(MessageBrokerRegistry registry) {
        registry.setApplicationDestinationPrefixes("/app");
        registry.enableSimpleBroker("/topic", "/queue");
        registry.setUserDestinationPrefix("/user");
    }
}

package com.example.realtime.chat;

import java.time.Instant;
import org.springframework.messaging.handler.annotation.MessageMapping;
import org.springframework.messaging.handler.annotation.Payload;
import org.springframework.messaging.handler.annotation.SendTo;
import org.springframework.stereotype.Controller;

@Controller
public class ChatMessageController {

    @MessageMapping("/chat.send")
    @SendTo("/topic/rooms.spring")
    public ChatMessageResponse send(@Payload ChatMessageRequest request) {
        return new ChatMessageResponse(
                request.roomId(),
                request.sender(),
                request.message(),
                Instant.now()
        );
    }
}

package com.example.realtime.chat;

public record ChatMessageRequest(
        String roomId,
        String sender,
        String message
) {
}

package com.example.realtime.chat;

import java.time.Instant;

public record ChatMessageResponse(
        String roomId,
        String sender,
        String message,
        Instant sentAt
) {
}

/ws
/app/chat.send
/topic/rooms.spring
/queue/notifications
/user/queue/notifications

package com.example.realtime.order;

import org.springframework.messaging.simp.SimpMessagingTemplate;
import org.springframework.stereotype.Service;

@Service
public class OrderStatusNotifier {

    private final SimpMessagingTemplate messagingTemplate;

    public OrderStatusNotifier(SimpMessagingTemplate messagingTemplate) {
        this.messagingTemplate = messagingTemplate;
    }

    public void notifyUser(String username, OrderStatusMessage message) {
        messagingTemplate.convertAndSendToUser(
                username,
                "/queue/order-updates",
                message
        );
    }
}