Top 3 Aggregation Interview Questions

Browse 3 real-world technical and behavioral interview questions about Aggregation. Review scenarios, edge cases, and architectural best practices.

A bundle can contain products or other bundles, and the pricing code should not care which it is holding. How would you model that?

A composite gives leaves and containers one interface so callers recurse without branching. The two decisions that matter are whether child management appears on that shared interface, and which operations genuinely aggregate - because price, availability and delivery date do not combine the same way. It also connects tree structures to the point an interviewer is testing.

mediumdesign

Adding a second LEFT JOIN doubled the revenue figure on a report. Explain what happened and write the correct query.

SQL join duplicates cause double counting when two one-to-many joins multiply rows before aggregation. Aggregate each child table to one row per parent first, then join those results back to the parent. Use this sql queries answer to show the decision, trade-off, and evidence rather than a memorised definition.

mediumcoding

You forecast every store and also the national total, and the store forecasts do not sum to it. What do you do?

Forecast at whichever levels have signal, then reconcile so the numbers are coherent by construction. Bottom-up preserves detail but accumulates noise, top-down is stable but allocates by an assumed proportion, and optimal reconciliation projects independent forecasts onto the set that adds up.

harddesign