Design in-memory threshold switcher
Company: Amazon
Role: Software Engineer
Category: System Design
Difficulty: hard
Interview Round: Technical Screen
Design an in-memory "switcher" component that toggles between ENABLED and DISABLED states based on runtime memory usage with user-configurable thresholds. Requirements:
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1) Support separate upper/lower thresholds (hysteresis) to prevent flapping.
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2) Allow dynamic reconfiguration at runtime without downtime.
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3) Provide thread-safe reads/writes and low-overhead sampling of memory metrics.
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4) Expose callbacks or events when state changes.
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5) Define behavior under memory spikes, metric polling failures, and multi-process or multi-instance deployments.
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6) Describe data structures, APIs, concurrency model, and monitoring/metrics.
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7) Discuss testing strategy, performance considerations, and trade-offs of pull vs push metric collection.
Overview: This question evaluates a candidate's ability to design memory-aware control systems, covering skills such as hysteresis-based thresholding, dynamic runtime reconfiguration, thread-safe concurrency, low-overhead metric sampling, event-driven state notifications, and handling multi-process and failure edge cases.
