Square data engineering interview questions are SQL-heavy, fintech-flavored, and PostgreSQL-grounded. Square rebranded to Block Inc. in December 2021, but the SQL bar — and the question shapes that show up in the live CoderPad pair-programming round — has not moved. Four primitives carry the loop: GROUP BY sender_id + COUNT(*) + ORDER BY DESC LIMIT 10 for top-N invoice senders, DATEDIFF / INTERVAL '30 days' cohort math for 30-day-post-signup activity windows, AVG(stars) OVER (PARTITION BY product_id, month) window aggregates for monthly product analytics, and COUNT(DISTINCT col) over status-filtered payment rows for fintech-grade transaction analysis. The framings are everyday Block / Square / CashApp data engineering — invoice ranking, cohort retention, monthly review averages, payment success counts.…