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Database / Google Spanner Database Interview questions

When would you choose bounded staleness over strong reads?

Bounded staleness tells Spanner "give me data that is at most N seconds old, but pick whatever timestamp lets you answer fastest," instead of forcing a strong read that must confirm it has the absolute latest commit before responding. Spanner is free to route the read to the closest available replica and serve it without waiting on the current leader.

This trade-off makes sense for read-heavy, latency-sensitive paths where near-real-time data is acceptable: a product catalog page, an analytics dashboard, or a recommendation feed rarely needs data that's only milliseconds old. Strong reads remain necessary whenever a read result feeds directly into a decision that must reflect the very latest write, such as checking current inventory right before finalizing a purchase.

What advantage does bounded staleness give Spanner when routing a read?
Which scenario still needs a strong read rather than bounded staleness?

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