Assess engineers beyond query correctness performance SQL. Practice SQL. Analyze performance. Hire with confidence.
1 -- Problem: Top customers by order value (5M rows) 2 -- Baseline: 842ms | Target: <80ms | Your score: 94 3 4 EXPLAIN ANALYZE 5 SELECT c.customer_id, c.name, 6 SUM(o.total_amount) AS total_spent, 7 COUNT(o.order_id) AS order_count 8 FROM customers c 9 JOIN orders o ON c.customer_id = o.customer_id 10WHERE o.created_at >= '2024-01-01' 11 AND o.status = 'completed' 12GROUP BY c.customer_id, c.name 13ORDER BY total_spent DESC 14LIMIT 100;
We focus on performance and optimization, not just correctness and helping the companies to hire the best.
Get scored on actual execution time, I/O cost, and plan quality — not just whether your result set matches. Run against 1M–10M row datasets that actually stress your query.
Interactive pg_flame-style SVG graphs of your execution plan. Click any node to drill into cost, rows, and time. Instantly see where your query bleeds time.
Compete globally or with friends. Earn badges like "Index God" and "Flame Master". Track streaks, skill heatmaps, and progress toward "DB Black Belt".
Join engineers who are learning what really happens inside their database — and getting measurably faster every week.
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