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Backend Engineer
Databases · Medium
8.0
Question
How would you design indexes for a high-traffic orders table?
Candidate answer
I would index customer_id and created_at because most queries filter by customer and sort recent orders first.
Strengths
- Explains indexes as a read-path optimization
- Mentions query patterns before choosing a data model
Weaknesses
- Does not quantify write overhead
- Misses when a compound index beats several single-column indexes
Model answer
Start from the query workload, add a compound index such as customer_id plus created_at for common reads, and measure write cost, storage, and cardinality before adding more indexes.