DynamoDB Indexing
A DynamoDB table can have two types of primary key,
- Simple primary key: Consist of a HASH key or partition key
- Composite primary key: Consist of two keys, HASH or partition key and RANGE or sort key
Partition keys used to determine, in which partition the item should be placed.
LSI & GSI
DynamoDB requires us to specify the primary key for all operations and hence provide faster performance.
We can scan on tables without primary key and it is not efficient and should avoid as much as possible.
LSI: Stands for local secondary index. We must create the LSI whenever we create table. After a table being created, we can not update the LSI. We can create up to 5 local secondary indexes. LSI supports both the eventual consistency and strongly consistency.
GSI: Stands for global secondary index. A global secondary index can be created with entirely new partition key and sort key. Supports maximum 20 GSI
- Global secondary index took a new partition and hence it needs a completely new throughput capacity for the RCU and WCU.
- GSI can be created anytime, not bound to the table creation time like the LSI.
- GSI can only perform eventual consistency
Sparse index is useful for querying over a small subsection of a table.