Read a page, keep the bookmark
Limit caps a page; LastEvaluatedKey is the bookmark you feed back to resume.
Why
This feed has nine posts and we want them four at a time. Limit caps a page at four, then the response carries a LastEvaluatedKey, the key of the last row it read. That is a resumable bookmark, not an offset.
Run the pages in order. Page two passes the bookmark back as ExclusiveStartKey and carries on. The last page returns one post and no LastEvaluatedKey at all: the missing bookmark is the end-of-results signal. There is no OFFSET in DynamoDB, and it never counts past where it stopped.
LastEvaluatedKey is a resumable bookmark, and its absence means the last page. Loop until the bookmark is gone, never on a count.
These rows are real and already here. Running an operation against them downloads a DynamoDB-compatible engine, about 850 KB, and executes it in this tab.
Limit 4 returns the first four posts. The response carries a LastEvaluatedKey: the key of the last row, your bookmark.
Run an operation to see the raw engine response.