DynamoDb table design: Single table or multiple tables

NoSql database is best suited for non-trasactional data. If you bring normalization(splitting your data into multiple tables) into noSQL, then you are beating the whole purpose of it. If performance is what matters most, then you should consider only having a single table for your use case. DynamoDB supports Range Keys, and also supports Secondary Indices. For your usecase, it would be better to redesign your table to use Range Keys. If you can share more details about your current table, maybe i can help you with more inputs.

FWIW, the AWS documentation on NoSQL Design for DynamoDB suggests to use a single table:

As a general rule, you should maintain as few tables as possible in a DynamoDB application. As emphasized earlier, most well designed applications require only one table, unless there is a specific reason for using multiple tables.

Exceptions are cases where high-volume time series data are involved, or datasets that have very different access patterns—but these are exceptions. A single table with inverted indexes can usually enable simple queries to create and retrieve the complex hierarchical data structures required by your application.