How to have an active flag in NoSQL without transaction

Question

This question is only for understanding purpose. This might be a noob question.

Assume that I have a tabular or document NoSQL database which do not support transactions. And I have a locations table/document which has an is_active column. A user can have multiple locations, but can have a SINGLE is_active:true location only. Now, if the user wants to

1. Change an is_active location, how do we handle it? As I need to set is_active false for 1 row and true for another
2. A use case where a user wants to create a new location for himself and set that location as is_active

How do I handle these logics without a transaction in a NoSQL? Do I need to model my tables in some other way?

Let's assume that:

1. I cannot use an SQL
2. I should not use transaction support provided by DBs like Mongo

NOTE: These might be a lot of assumptions and might not be real-world use cases. But I am just trying to understand HOW we should model NoSQL databases.

Answer 1

This is a typical data modelling question for nosql systems. I won't put here the whole theory, but these are links to check: https://docs.aws.amazon.com/amazondynamodb/latest/developerguide/bp-relational-modeling.html and https://cassandra.apache.org/doc/latest/cassandra/data_modeling/index.html

The key take away is that you don't want to create a normalized version of SQL like db in a nosql system. In your particular case, you have to explore access patterns for reads and writes; and that will help you to define you data structures. For example, you may want to get rid of "locations" table and keep those as properties of users - this is almost classical use case in nosql world.