Databaseshard

What is a materialized view and when would you use it?

Answer

A materialized view stores the result of a query physically, so reads can be much faster than recomputing the query each time. You use it for expensive aggregations or reporting, accepting the trade-off: refresh cost and (often) slightly stale data.

Advanced answer

Deep dive

Expanding on the short answer — what usually matters in practice:

Context (tags): views, materialized-view, performance, reporting
Data model and access patterns: dominant queries (read/write ratio, sorting, pagination).
Indexes: when they help vs hurt (write amplification, memory).
Consistency & transactions: what’s guaranteed and what can bite you.
Explain the "why", not just the "what" (intuition + consequences).
Trade-offs: what you gain/lose (time, memory, complexity, risk).
Edge cases: empty inputs, large inputs, invalid inputs, concurrency.

Examples

A tiny example (query shape):

-- Example: index + query shape
SELECT *
FROM users
WHERE email = '[email protected]'
LIMIT 1;

Common pitfalls

Too generic: no concrete trade-offs or examples.
Mixing average-case and worst-case (e.g., complexity).
Ignoring constraints: memory, concurrency, network/disk costs.

Interview follow-ups

When would you choose an alternative and why?
What production issues show up and how do you diagnose them?
How would you test edge cases?