In the course – Dynamo DB slide – exactly at 9:45 – in the table 4th point specifies it improves writes ? How will it improve the performance of writes?
Good question. I’m uncertain how/if it improves writes to be honest. You don’t write directly to an index (as stated in the docs).
Check out this AWS blog on the topic: https://aws.amazon.com/blogs/big-data/scaling-writes-on-amazon-dynamodb-tables-with-global-secondary-indexes/