AWS Certified Data Engineer Associate DEA-C01 Practice Question

The most efficient design stores all readings for the same device in one partition and sorts them by timestamp. A query that specifies the deviceId and a timestamp condition can retrieve the last 24 hours without scanning other partitions. A global secondary index with readingType as the partition key and timestamp as the sort key supports lookups for a reading type across all devices. Adding a TTL attribute based on timestamp automatically removes stale data, keeping partitions small and lowering read costs. Designs that put readingType in the base table's key, omit an index, or create many daily tables either force application-side filtering or require multiple queries, resulting in higher read cost and operational overhead.