primary-key-design

I'm currently in the process of designing the database tables for a customer & website management application. My question is in regards to the use of primary keys as functional parts of a table (and not assigning "ID" numbers to every table just because). For example, here are four related tables from the database so far, one of which uses the traditional primary key number, the others which use unique names as the primary key: -- -- website -- CREATE TABLE IF NOT EXISTS `website` ( `name` varchar(126) NOT NULL, `client_id` int(11) NOT NULL, `date_created` timestamp NOT NULL default CURRENT

I've read lots of DynamoDB docs on designing partition keys and sort keys, but I think I must be missing something fundamental. If you have a bad partition key design, what happens when the data for a SINGLE partition key value exceeds 10GB? The 'Understand Partition Behaviour' section states: "A single partition can hold approximately 10 GB of data" How can it partition a single partition key? http://docs.aws.amazon.com/amazondynamodb/latest/developerguide/GuidelinesForTables.html#GuidelinesForTables.Partitions The docs also talk about limits with a local secondary index being limited to 10GB

I'm trying to determine the best way to deal with a composite primary key in a mongo db. The main key for interacting with the data in this system is made up of 2 uuids. The combination of uuids is guaranteed to be unique, but neither of the individual uuids is. I see a couple of ways of managing this: Use an object for the primary key that is made up of 2 values (as suggested here ) Use a standard auto-generated mongo object id as the primary key, store my key in two separate fields, and then create a composite index on those two fields Make the primary key a hash of the 2 uuids Some other