When should you NOT use a skip list instead of a balanced tree?

Use a tree if you need strict O(log n) worst-case guarantees and can afford the complexity. Use a tree if you need parent pointers for range deletions or efficient reverse traversal. Skip lists win when you prioritize simplicity, concurrent inserts, or range scans (you just walk the base level). Most databases choose skip lists for in-memory work (transient, high churn); trees for persistent storage (predictable latency, stability).

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