This was basically seven questions dressed up as one.
Start by clarifying requirements and constraints, then propose a modular design with a clear state machine, thread-safe state management, and configurable hysteresis. Walk through the core components, discuss trade-offs (e.g., polling vs. event-driven, lock granularity), and address edge cases like spikes, failures, and multi-instance coordination.
Pro tip: Emphasize observability: include metrics, logging, and health checks for the switcher's state and transitions. This shows you think beyond functionality and consider operational excellence, which is highly valued at Amazon.
Ask questions to understand expected memory metrics (e.g., heap usage, RSS), threshold units, hysteresis parameters, callback semantics, and multi-instance deployment (e.g., shared state or independent).
Design a state machine with ENABLED and DISABLED states, transitions triggered by memory thresholds with hysteresis. Define a thread-safe API for state queries, configuration updates, and callback registration.
Choose synchronization primitives (e.g., atomic references, read-write locks) to ensure thread-safe reads/writes and avoid contention. Consider using immutable state objects for atomic updates.
Allow dynamic updates to thresholds and hysteresis without restart. Implement a callback mechanism (e.g., listener pattern) to notify state changes, ensuring callbacks are invoked outside locks to prevent deadlocks.
Define behavior for memory spikes (e.g., debouncing), polling failures (e.g., fallback to last known state or safe default), and multi-instance deployments (e.g., using a distributed cache or consensus for shared state).
AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.