Problem Solving and Database Round

What they ask

An online technical interview that mixes a problem-solving exercise with database questions, followed later by an engineering manager conversation.

Problem-solving sample (solve in the starter code): delivery slots are given as [start, end] minute intervals for one rider; merge overlapping or touching slots so the rider has the fewest continuous windows.

Database questions in this area, for example:

• Write a query for the top 5 products by revenue per day over the last week.
• What index would you add for "orders by customer, newest first", and why a composite index order matters.
• Normalization: when you would denormalize an orders table for reporting.
• Transactions: what isolation level prevents two checkouts from overselling the last unit.

Examples

• [[0,30],[5,10],[35,50],[50,60]] returns [[0,30],[35,60]].
• [[10,20]] returns [[10,20]].

Constraints

• Up to 10^4 intervals; O(n log n) via sorting is expected.

What they look for

• Sorting by start and a single sweep, with the touching-interval case handled (50 meets 50).
• Practical SQL: joins, aggregates, and indexing reasoning.
• Clear communication; the interviewer shares screen and asks you to narrate.