Indexes

• Indexes create an alternative view of the table
• There are 2 types of Indexes namely Local Secondary Index (LSI) & Global Secondary Index(GSI)
• GSI allows to create a view using a different Partition and Sort Key
• Some or all attributes can be projected in these indexes
• AWS recommends to use GSIs by default and use LSI only where Stron Consistency is required

Local Secondary Index (LSI)

• Created by using alternate Sort Key
• LSI allows to create a view using a different Sort Key
• Must be created with the Table
• Max 5 LSIs per table are allowed
• Shares the RCU & WCU of base table
• Either ALL or Keys Only or specific Attributes can be projected in the LSI
• Indexes are sparse indexes i.e. only items which have the attribute which LSI is projecting as non blank not null are part of LSI

Global Secondary Index(GSI)

• Can be created by using an alternate Partition Key & Sort Key
• Can be created anytime during Table's life cycle
• By defaul 20 GSI/Per table are allowed
• Uses its own WCU & RCU different than Table's
• One can choose which attribute can be projected in the GSI
• GSIs are always eventually consistent