DynamoDB database model for storing different objects

I'm trying to learn DynamoDB just for didactic purposes, for that reason I propose myself to create a small project to sell vehicles (cars, bikes, quad bikes, etc) in order to learn and get some experience with NoSQL databases. I read a lot of documentation about creating the right models but I still cannot figure out the best way to store my data.

I want to get all the vehicles by filters like:

• get all the cars not older than 3 months.
• get all the cars not older than 3 months by brand, year and model.
• And so on the same previous queries for bikes, quad bikes, etc.

After reading the official documentation and other pages with examples (https://docs.aws.amazon.com/amazondynamodb/latest/developerguide/bp-general-nosql-design.html#bp-general-nosql-design-approach , https://medium.com/swlh/data-modeling-in-aws-dynamodb-dcec6798e955 , Separate tables vs map lists - DynamoDB), they said that the best designs use only one table for storing everything, so I end up with a model like the next below:

-------------------------------------------------------------------------------------
Partition key |          Sort key     | Specific attributes for each type of vehicle
-------------------------------------------------------------------------------------
    cars      | date#brand#year#model | {main attributes for the car}
    bikes     | date#brand#year#model | {main attributes for the bike}
-------------------------------------------------------------------------------------

I've used a composite sort key because they specify that is a good practice for searching data (https://docs.aws.amazon.com/amazondynamodb/latest/developerguide/bp-sort-keys.html).

But after defining my model I end up that the previous model will have a problem called "Hotspotting" or "Hoy key". (https://medium.com/expedia-group-tech/dynamodb-data-modeling-c4b02729ac08, https://dzone.com/articles/partitioning-behavior-of-dynamodb) because in the official documentation they recommend having partitions keys with high cardinality to avoid the problem.

So at this point, I'm a little stuck about how to define a good and scalable model. Could you provide me some help or examples about how to achieve a model to get the queries above mentioned?

Note: I also considered creating a specific table for each vehicle but that would create more problems because to find the information I would need to perform a full table scan.