What methods are used for synchronous interaction between microservices?

Synchronous interaction between microservices is usually carried out through:

1. HTTP/REST API — the most common method, where one service makes an HTTP request to another and waits for a response.
2. gRPC — a high-performance remote procedure call protocol supporting synchronous calls with protobuf-based contracts.
3. SOAP — less common now, but also an option for synchronous interaction via web services.

Example in Python using requests for REST:

import requests

def get_user_data(user_id):
    response = requests.get(f'http://user-service/api/users/{user_id}')
    if response.status_code == 200:
        return response.json()
    else:
        raise Exception('Error fetching user data')

In synchronous interaction, it is important to consider delays and fault tolerance, as the call blocks execution until a response is received.