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The core structure wasn't hard to land on, a map of maps basically.
Start by clarifying the requirements: the database must support set, get, and delete operations on key-field-value triples with O(1) average time. Propose a nested hash map structure: an outer map from keys to inner maps, where each inner map stores field-value pairs. Then discuss implementation details, trade-offs, and potential extensions.
Pro tip: Mention that while average O(1) is achievable with hash maps, worst-case O(n) can occur due to collisions; briefly discuss how to mitigate (e.g., using balanced trees or consistent hashing) to show depth. Also, consider memory overhead and concurrency if relevant.
Ask about expected data volume, concurrency needs, persistence, and whether fields are unique per key. Confirm that O(1) average time is the goal and discuss acceptable trade-offs.
Suggest a hash map of hash maps: outer map keyed by the primary key, inner map keyed by field name with value as the field value. This allows O(1) average set, get, and delete for a given key and field.
Explain how each operation works: set inserts or updates the inner map; get retrieves the inner map then the field; delete removes the field and optionally the key if the inner map becomes empty.
Discuss average O(1) time for all operations, worst-case O(n) due to collisions, and memory overhead. Mention alternatives like using a single map with composite keys (key+field) but note that nested maps better support field-level operations.
Address concurrency (e.g., using locks or concurrent hash maps), persistence, and additional operations like getting all fields for a key. Discuss handling of null values and deletion of non-existent keys/fields.
AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.