Implement cluster status tracker

Q: Implement cluster status tracker

This question evaluates a candidate's competence in data structures and algorithms for time-ordered state tracking, time-series indexing, conflict resolution (last-write-wins), memory-efficient storage, and concurrent system behavior under high update rates.

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Question

Implement a cluster status tracker. Design a class with methods: update(nodeId, status, timestamp) to record node status updates that may arrive out of order or be duplicated; getCurrent(nodeId) to return the most recent status; getAt(nodeId, t) to return the status effective at time t; getClusterSummaryAt(t) to return counts of nodes by status at time t, where a node is considered OFFLINE if it has not reported in the last TTL seconds. Use last-write-wins by (timestamp, nodeId) for conflict resolution. Aim for O(log n) per update/query and memory efficiency for up to 100k nodes and 10M updates/day. Describe data structures (e.g., per-node ordered maps, indexes for aggregation), handling of out-of-order events and idempotency, and a strategy to compact/expire historical data. Follow-ups: (

add range queries (e.g., counts per minute over the last K minutes) efficiently; (
make updates and reads thread-safe under high concurrency, discussing sharding and lock strategies.

Implement cluster status tracker

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