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Database Scaling — Series 3
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A database supports covering indexes. A frequent query filters by customer_id and returns only order_id and total. Which index can satisfy its required columns without a separate table lookup when visibility permits?
AAn index on total including the creation timestamp.
BAn index on customer_id including order_id and total.
CAn index on order_id including the creation timestamp.
DSeparate indexes on total and the creation timestamp.
A large append-only table is partitioned by month. Entire old months expire together. What usually removes an expired month's data with less row-by-row work?
ACopy current rows into the same expired partition.
BDelete each expired row through a secondary index.
CDetach or drop the expired partition.
DMark each expired row with a soft-delete flag.
A table has daily range partitions on created_at. A query for one day scans all partitions because its predicate wraps the key in an unsupported function. What is the most targeted fix?
ASort the query output by created_at.
BUse a supported half-open range on created_at.
CAdd more partitions with smaller date ranges.
DIncrease the number of database replicas.
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