sortkey in DynamoDB query with pagination limit

Question

I have a doubt that when we use sortkey in DynamoDB query with pagination limit(example limit=10), whether it gives a sorted list of 10 items of an entire dynamoDB table or just gives the queried items sort list?

If it only gives sort list of queried items how to get the sort list of total dynamoDB table items?
for example there is a post table & post has likes how to get the post with highest likes in the table with list of posts in descending order?

Accepted Answer

Its not possible to obtain order over all keys in a DynamoDB table. The only possible approach would be to `Scan` the entire table and implement your sorting on the client side.

You could of course use DynamoDB Streams and keep pointers to the top 10 liked posts, if that is something your application intends to show. Then you could simply call `BatchGetItems` with the 10 listed items.

Another option would be to create a GSI with a single attribute as the PK, for example `POSTS` and the number of likes as the SK. 
| PK | SK | Other |
| --- | --- | --- |
| POSTS | 7 | Data |
| POSTS | 9 | Data |
| POSTS | 11 | Data |

Then you could simply `Query` your GSI with the key `POSTS` and use `ScanIndexForward=False`, `Limit=10`.

*Be warned that this is not a scalable solution as your GSI key is a single value. This will limit your tables writes to approximately 1000WCU per second. That's a decision you can make depending on your throughput needs.*

sortkey in DynamoDB query with pagination limit

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