aws dynamodb indexes

DynamoDB indexes exist to allow querying on non-primary key attributes stored within the table.

Flexible querying

Query based on an attribute that is not the primary key. This uses global secondary indexes and local secondary indexes to accomplish query execution.

• Secondary index - allows you to perform fast queries on specific columns in a table.
  • You select the columns that you want included in said index, then run the searches
  on the index itself rather than the whole dataset. These run on a subset of the data.

Local secondary index

• Primary key - These have the same partition key as the original table, but a different sort key.

This changes the organization of the data, but still uses the original table partition.

• Different view - gives a different view of the data due to the alternate sort key
• Faster queries - Any queries fbased on this sort key are much faster using the index

rather than the maint able. * Example: Partition key of user ID, sort key of account creation date

• Added at creation time - The local secondary index can only be added when you are

creating your table. These cannot be added, removed, or modified later.

Global secondary index

• A completely different primary key - different partition and sort keys
• View data differently - also gives a different view of the data (similar to local secondary index)
• Speeds up queries - the speed is related to the alternative partition and sort key
  • Example: Parititon key of email address, sort key of last login date
• Flexible - You can create these when you create or table, or add them in later.

Exam tips

• Enable fast queries on specific data columns
• Give a different view of the data based on an alternative parition/sort key combination
• Each index type offers different benefits, these should be considered on table creation