Amazon·Software Engineer·Technical Phone Screen·Intermediate

Intermediate

May 2026

Summary

Amazon SWE interview with a SQL problem focused on finding users who signed up in a date range but never placed an order during that same window. Pretty standard left join territory but the edge cases around order dates outside the range are where things get interesting.

Questions Asked (1)

Given a users table and an orders table, write a SQL query to return users who signed up in January 2025 but placed zero orders during that same period. Results should be ordered by user_id ascending, and the solution needs to handle tables with up to 10 million rows each.

Data ModelingTechnical Trade-offsAlgorithms & Data Structures

Author's notes

The tricky part isn't the join itself, it's the date scoping on the orders side.

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AI HintsAI Generated

Suggested Approach

Use a LEFT JOIN or NOT EXISTS to find users who signed up in January 2025 and have no orders in that period, ensuring the query is sargable and leverages indexes. For large tables, prefer NOT EXISTS with proper indexing on orders.user_id and orders.order_date to avoid full scans.

Pro tip: Mention that you would verify the execution plan and consider partitioning or indexing strategies, as Amazon values scalability and performance tuning for large datasets.

1. Clarify requirements and schema

Confirm the table structures, date ranges, and that 'zero orders' means no orders at all in January 2025, not just no orders after signup.

2. Choose the right SQL pattern

Select between LEFT JOIN with IS NULL, NOT EXISTS, or NOT IN, considering performance and NULL handling for large tables.

3. Write the query with performance in mind

Use sargable predicates, ensure indexes on user_id and order_date, and avoid functions on columns in WHERE clauses.

4. Validate and optimize

Check the execution plan, consider adding a composite index on orders(user_id, order_date), and test with large data volumes.

Key Points to Mention

Use of NOT EXISTS or LEFT JOIN with IS NULL to find users without orders
Importance of sargable date filters (e.g., signup_date >= '2025-01-01' AND signup_date < '2025-02-01')
Indexing strategy: index on users(signup_date) and orders(user_id, order_date)
Handling NULLs correctly when using NOT IN (avoid if subquery can return NULLs)
Scalability considerations: partitioning, query plan analysis, and avoiding full table scans
Ordering by user_id ascending as specified

AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.