Esse é um exemplo que faz requisição do blob de três imagens comprimidas em base64 no banco dos EUA em mongoDB

Requisicao-sem-threads.py

#!/usr/bin/python3
# -*- Coding: utf-8 -*-
from flask import Flask, jsonify
from pymongo import MongoClient
import os

app = Flask(__name__)

# Conectio my 
client = MongoClient('mongodb://example:senha@host.com/images',45704)
db = client.images                                                       
                                                                         
# API work                                                               
@app.route('/')                                                          
def main ():
    # Selecting colletion
    collection = db['blobs']
    #cursor = collection.find({})
    
    def make(x):
        # The values get information by type
        return 'Fuckindata {"buf":"'+str(collection.find_one({"type":x})["data"])+'"}' 

    # Make a loop in cursor, in collection
    blob = list(map(make,['a','b','c']))
    print (blob)
    return jsonify(blob)