Skip Lists

Imagine you're building a high-performance database that needs to handle millions of concurrent reads and writes per second.

You need a data structure that maintains sorted order, supports efficient range queries, and can handle many threads accessing it simultaneously without locking the entire structure.

Balanced trees like Red-Black trees or AVL trees seem like natural choices. They offer O(log n) operations and maintain sorted order.

But there's a problem: when multiple threads try to modify the tree concurrently, rebalancing operations can cascade through large portions of the tree, requiring complex locking mechanisms that destroy performance.

This is where Skip Lists come in.

Invented by William Pugh in 1989, Skip Lists have become the backbone of some of the most widely-used distributed systems, including Redis, LevelDB, RocksDB, and Java's ConcurrentSkipListMap.