A partition key is the primary key attribute that DynamoDB hashes to decide which physical partition stores an item. In a table with only a partition key, each value must be unique.
It matters for three reasons:
The hash spreads items across partitions without any setup.
Values with an even share of traffic avoid a hot partition, one partition that takes most requests and throttles.
As data and traffic grow, DynamoDB adds partitions, and an even key spreads the load across them.
In a users table, user_id as the partition key spreads users evenly across partitions.
Rewriting in plainer words…
This answer doesn't lend itself to a diagram - it reads best . No credits were charged.
