My first instinct was a simple incrementing counter and i ran with it for a bit before they nudged me toward deallocation.
Start by clarifying requirements: what is a server number, how many server types, expected request rate, and constraints on number reuse. Then propose a design using separate pools per server type, each implemented with a min-heap or a free-list for efficient allocation and deallocation, and discuss trade-offs between different data structures.
Pro tip: Mention that you would use a min-heap to always allocate the smallest available number, which helps with predictability and debugging, and that you would consider a bitset for dense pools to save memory and improve cache performance.
Ask about the definition of server numbers, the number of server types, expected scale, and whether numbers should be reused or monotonically increasing. Also clarify concurrency and persistence needs.
Propose a separate pool per server type. For each pool, use a min-heap of available numbers for O(log n) allocation and deallocation, or a free-list with a stack for O(1) if order doesn't matter. Discuss memory vs speed trade-offs.
Describe the allocate operation: pop from the heap (or pop from stack) and assign to request. For deallocate, push the number back. Ensure thread safety with locks or lock-free structures if needed.
Discuss partitioning pools by server type and possibly sharding further. Mention using concurrent data structures or per-thread pools to reduce contention. Consider persistence for recovery.
Compare min-heap vs bitset vs free-list in terms of time/space complexity. Discuss handling of number exhaustion, dynamic pool resizing, and monitoring.
AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.