How many records should I aim to put into a DynamoDb partition?
I'm designing a table which will store about a thousand records per user where the PK is the user's id. The average record size is about 500 bytes. How can I know if I have 'too many' records?
You can never have too many records, feel free to store as many as you like.
One caveat to that is if you use a Local Secondary Index (LSI), in which case data related to a user would not be able to exceed 10GB. 99.99% of people don't require a LSI so you should have no issue also.