How to make Flask method thread safty

I have the following Flask code:

from flask import Flask

active_ids = {}

@app.route('/',methods=['GET','POST','DELETE'])
def serve():
    request_id = request.cookie['id']
    
    if request_id not in active_ids:
        # do my logic
    
if __name__ == '__main__':
    app.run(host="0.0.0.0")

The function serve is thread safty? If not, what is the best why to make it?