Records in the database are sequenced with sort key, let alone this, What you see records are serially sequenced, same sequence will retain if record is same for every query, Thus in that Query lastEvalautedKey tells you that data is fetched up to this key (exluding lastEvalluatedKey) For Next Query It takes data from this key and appends to what returned earlier in do while loop mechanism. Records are pushed in array thus query executing again will return record and we push it in array.