Why DynamoDB scan with Limit and FilterExpression not return the items that match the filter requirements?

From the docs that you quoted:

If you also supply a FilterExpression value, DynamoDB will return the items in the first six that also match the filter requirements

By combining Limit and FilterExpression you have told DynamoDB to only look at the first two items in the table, and evaluate the FilterExpression against those items. Limit in DynamoDB can be confusing because it works differently from limit in a SQL expression in a RDBMS.

Also ran into this issue, i guess you will just have to scan the whole table to a max of 1 MB

Scan The result set from a Scan is limited to 1 MB per call. You can use the LastEvaluatedKey from the scan response to retrieve more results.

http://docs.aws.amazon.com/amazondynamodb/latest/developerguide/Limits.html