Design a Cloud Bigtable row key for data migrated from MySQL. Which row key should you use?

The correct row key is AccountidEventtimestamp. Bigtable stores data lexicographically by row key, so designing a key that groups related data together is crucial for efficient queries. By starting with Accountid, all events for a specific account are stored contiguously, making queries for an account's activity very fast. Appending Eventtimestamp allows for efficient retrieval of events within a time range for that specific account. Using Accountid alone would make it difficult to query for specific events or time ranges within an account. Eventtimestamp alone would scatter an account's events across the table, making per-account queries inefficient. EventtimestampAccountid would group events by timestamp first, which is generally less useful for typical application queries that focus on a specific account's history.