Hi
Disclaimer: I am in no way affiliated with https://www.kamatera.com/ - and have not (nor will I) receive any kind of compensation for this recommendation.
If you need a cheap mongoDB - suited for Squidex - I can highly recommend hhttps://www.kamatera.com/express/compute/apps.php#app=MongoDB
It was really easy to set up - and you actually get the first month for free 
The performance is excellent - It is actually faster than https://www.mongodb.com/ (and cost a fraction)