Which statement about the relationship between SQL databases and a key-value store is accurate?

Which statement about the relationship between SQL databases and a key-value store is accurate?

• A. A key-value store is often used alongside SQL as a cache for hot data, with SQL as the source of truth.
• B. A key-value store replaces SQL as the primary data model.
• C. A key-value store enforces foreign keys across tables.
• D. A key-value store automatically provides rich query capabilities.

Answer: (A)

Key concept: using a fast key-value store as a cache alongside a primary SQL database. In many systems, the SQL database acts as the source of truth, handling complex queries and relationships, while a key-value store (often in memory) caches hot data to deliver ultra-fast reads and reduce load on the SQL database. This cache-aside or write-through setup lets frequently accessed items be retrieved quickly, with the SQL store remaining the authoritative location for updates and long-term persistence. The other statements stray from common practice: a key-value store doesn’t usually replace SQL as the primary data model because it lacks rich querying and relational constraints; it doesn’t enforce foreign keys across tables; and it doesn’t inherently provide rich query capabilities.

Key concept: using a fast key-value store as a cache alongside a primary SQL database. In many systems, the SQL database acts as the source of truth, handling complex queries and relationships, while a key-value store (often in memory) caches hot data to deliver ultra-fast reads and reduce load on the SQL database. This cache-aside or write-through setup lets frequently accessed items be retrieved quickly, with the SQL store remaining the authoritative location for updates and long-term persistence. The other statements stray from common practice: a key-value store doesn’t usually replace SQL as the primary data model because it lacks rich querying and relational constraints; it doesn’t enforce foreign keys across tables; and it doesn’t inherently provide rich query capabilities.