Explain hash map internals and edge cases

You are asked a “knowledge check” about hash maps (hash tables). Discuss how a typical in-memory hash map works and how you would reason about these edge cases: - Collision handling strategies and their trade-offs. - Load factor, resizing/rehashing, and amortized complexity. - Handling deletions (especially in open addressing). - Worst-case behavior and how to mitigate it. - Iteration order and how it can change. - Concurrency concerns (reads/writes) and common approaches to thread safety. Assume a general-purpose language runtime hash map (e.g., Java/C++-like), not a distributed store.