Items in DynamoDB are simply collections of attributes. Attributes can be in the form of strings, numbers, binaries, or a set of scalar attributes. Each attribute consists of a name and a value. An item must have a primary key. As we have already seen, a primary key can have a hash key or a combination of hash and range keys. In addition to the primary key, items can have any number of attributes except for the fact that item size cannot exceed 64 KB.
While doing various item operations, you should have be aware of following DynamoDB features.
In Chapter 1, Getting Started, we had talked about the durability feature of DynamoDB. To provide this durability, DynamoDB keep copies of items in various availability zones. When a certain item gets updated, DynamoDB needs to make sure that it updates all other copies as well. However, it takes time to make any write consistent on all servers; that's why the operation is called eventually consistent...
