Seemed simple at first and I almost said 'just use a hashmap' before catching myself.
Start by clarifying requirements (e.g., single-threaded vs concurrent, memory constraints) and then propose a hash map with timestamped entries, using lazy eviction or a background thread to remove stale entries. Discuss trade-offs between time-based eviction strategies and data structures, and consider edge cases like clock skew and high throughput.
Pro tip: Mention that you would use a monotonic clock (e.g., System.nanoTime()) instead of wall-clock time to avoid issues with system time changes, and discuss how to handle concurrency with minimal locking (e.g., ConcurrentHashMap with compute()).
Ask about expected throughput, concurrency, memory limits, and whether the cache should be distributed. Confirm that 'within the past 10 seconds' means a sliding window from the last print.
Propose a hash map (or concurrent map) storing the last print timestamp for each value. For eviction, consider a min-heap or a time-ordered queue to efficiently remove expired entries.
Decide between lazy eviction (check on access) and active eviction (background thread). Discuss trade-offs: lazy is simpler but may retain stale entries; active keeps memory bounded but adds complexity.
If multi-threaded, use thread-safe structures and atomic operations. Consider lock striping or read-write locks to minimize contention. Ensure that the check-and-update is atomic.
Discuss time complexity (O(1) average for check/update), memory usage, and potential issues like clock skew, high cardinality, and bursty traffic. Suggest monitoring and tuning parameters.
AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.