A probabilistic set that answers "definitely NOT in set" or "POSSIBLY in set" — never false negatives, allows false positives.

A tree of hashes where each parent = hash(left child + right child) -- detect exactly which data blocks differ between two systems in O(log n).

Feedback is the mechanism by which people grow. The manager who avoids giving hard feedback because they care about people actually cares more about their own comfort than the person's growth.

Process sequential data in O(n) with a moving window -- the core algorithm for streaming analytics, rate limiting, and network protocols.

Self-balancing tree keeping data sorted with O(log n) reads/writes -- the dominant index structure in relational databases.

Graphs model relationships -- social networks, dependencies, routing, recommendations. Knowing when to apply each traversal is the key system design skill: BFS for unweighted paths, Dijkstra for weighted, topological sort for DAGs.

The 1:1 is the manager's highest-leverage recurring meeting. Done well, it's the primary vehicle for trust, feedback, career growth, and early problem detection. Done poorly -- or skipped -- it signals that the person doesn't matter.

Log-Structured Merge Tree -- optimise for write-heavy workloads by batching writes in memory then flushing sorted to disk. Reads pay the cost.

Divide search space in half each step -- O(log n) on any sorted or monotonic space. Far more powerful than sorted array lookups: query optimization, version control, logging systems, and rate limiting.

The single highest-leverage activity a manager does. One great hire creates more value than a hundred process improvements. One bad hire costs 1.5-3x their annual salary and poisons team dynamics for months.