Need help/advice on backend choice and data model for an IOS app.

Basically for my app I need to implement UI with folder like structure and hence need to store hierarchal data in a database. see example in attached image. However I dont need to store references to files but rather actual json objects/documents (or references to them?). So I am looking for somebody to assist me with help/advice on how it could be implemented. More Requirements below: 1. Folder names should be unique inside its parent folder. 2. Json Object names should be unique inside its parent folder. 3. I should be able to Add, Rename, Move, Copy, Delete folder with its subfolders/documents. 4. IMPORTANT: providing 1,2 are satisfied I should be able to query object data via their names path. For example i want to query/filter all the users whose age are >18, Name = John and [login to view URL] = Bob useing the below paths(if data exists there) *USERUNIQUEID*/allData/Personal Data/Age *USERUNIQUEID*/allData/Personal Data/Name *USERUNIQUEID*/allData/Pets/Cats/CatsJsonObject Some of my thoughts regarding db choices/designs: 1) Relational Databases (SQLite): there are some ways to model hierarchal data [login to view URL] However not sure if i would be able to easily query the way i want. 2) Firebase - json tree could store deep nested data however no native way of doing complex queries therefore i wold have to write some complex logic on client side (aka multiple requests for each filter condition). Also it downloads the whole json tree for a child... 3) Firestore - i am able to use complex queries providing put all user data as documents into one collection. So every document would have ParentFolderId field. Problem here is that the path to a document would be made of Firestore generated unique ids (because document titles are only unique under its parentFolder so not possible to use as a document id) [login to view URL] 4) Couch Db? not sure if this NoSql document store provides any advantage comparing to firestore solution. [login to view URL] Ideally if you have implemented something like this in the past and are based in the UK.