Interview Quiz

Example Questions From the Test

• 1A replicated store has N=3 copies, a successful write requires W=2 acknowledgments, and a read consults R=2 copies. Why can this configuration help a read encounter the latest acknowledged write, assuming completed quorum operations and proper version handling?
  • Because the read and write quorums must overlap when R + W is greater than N
  • Because every write is sent to exactly the same single replica
  • Because asynchronous networks always deliver writes in timestamp order
  • Because three replicas eliminate the possibility of node failure
• 2A payment client retries a request after timing out, even though the first request may have succeeded. Which design most directly prevents a duplicate charge?
  • Increase the client timeout for every payment request
  • Place payment requests on a higher-priority network connection
  • Associate the operation with an idempotency key and reuse its recorded result
  • Create a new transaction identifier for every retry attempt
• 3One database server can no longer hold a growing customer dataset or sustain its write volume. Which technique distributes different subsets of the data across multiple servers?
  • Replicating the complete dataset to read-only followers
  • Sharding the data by a suitable partition key
  • Adding a local in-memory cache to the existing server
  • Archiving the database transaction log more frequently