Back4app is a really great service for when you quickly want to get started with a prototype for an app/site that needs a backend/database. The parse database is very flexible so you can work out your data structure as you go. Support for live queries (real time updates) is great for things like chat, but I believe this requires the paid subscription nowadays. First level subscription is 25$ per month, which is quite ok. Free tier gives you enough for getting started with low amount of queries and data storage (1gb). The cloud code is also a really nice feature, so you can have code running on their server. I've used it for example to relay calls to an external API and back, and schedule tasks. Support is willing to answer your questions in good time, and they are quite good in helping out. A relatively new feature is also the possibility to run docker containers, pretty sweet! All in all back4app is my go-to solution for very quickly starting a prototype combined with a quasar frontend.

Excellent backend solution, it perfectly meets the requirements.

The back4app library is great to access and create data in the database. Saves a lot of time and hassle required to make a backend for mobile apps.