Databases · Senior · Question 23 of 75

What makes a good shard key?

1A timestamp, so new data goes to one shard
2A boolean column
✓Correct answer: High cardinality, even distribution of data and load, and alignment with the most common queries (e.g. tenant ID)

Explanation

A time-based key sends all new writes to one shard (a hotspot). Queries that cross shards are expensive, so keep a tenant's data together.

Further reading

Test yourself

Take the Databases · Senior quiz: questions and options are shuffled, and you get a review of your mistakes at the end.