Can you please provide an example of local secondary key?
I think you’re referring to a Local Secondary Index? Let’s say that you already have the partition key but you want to quickly look up records by another value too. The example in the lecture is a Sales Order table where the Sales Order number is the partition key. If you have the Sales Order number but let’s say the sales order has 1000 line items, it would be expensive to retrieve all 1000 line items then parse through them to find only those with a certain part number.
We can create a local secondary index where we pass in the Sales Order number and the part number to efficiency get back only those line items with the part we’re after.