I started with get/put/delete and felt pretty good about it, then they pushed on contains and size and I realized I hadn't thought through atomicity at all.
Start by defining a minimal, thread-safe API (get, put, delete) with clear semantics for missing keys and null values. Then discuss concurrency strategies like fine-grained locking or ConcurrentHashMap, and finish by acknowledging limitations such as no persistence, no eviction, and memory constraints.
Pro tip: Proactively mention that a hash map alone cannot support range queries or ordered iteration, and suggest how you'd extend it (e.g., with a skip list) if needed—this shows you understand trade-offs beyond the immediate ask.
Specify methods like get(key), put(key, value), delete(key), and containsKey(key). Clarify behavior for null keys/values, missing keys, and whether operations are atomic.
Discuss handling of null keys (e.g., disallow or use a sentinel), null values (e.g., treat as delete or store), and concurrent modifications during iteration.
Choose a concurrency strategy: synchronized methods, read-write locks, or ConcurrentHashMap with atomic operations. Explain trade-offs in throughput and complexity.
Highlight that a hash map alone lacks persistence, eviction policies, range queries, and scalability beyond a single node. Mention memory overhead and hash collisions.
If time permits, suggest how to add TTL, LRU eviction, or persistence, and note the additional data structures or systems required.
AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.