Microsoft OOD Question: Real-Time Car Simulation System

You are asked to design a Real-Time Car Simulation and Monitoring System used by a vehicle manufacturer for internal testing. The system should simulate many independent car instances concurrently and provide real-time status updates (startup state, door positions, component temperatures), event logging, and a dashboard for queries. You will need to model car state transitions (ignition -> running, doors open/closed/locked), emit events for telemetry, and support concurrent user actions on the same car.

Start by outlining the high-level flow: a simulation engine produces events per car, events are published to an event bus or message queue, workers process events and update the car state (and persistent event log), and real-time subscribers (dashboards, alerting) consume updates via WebSockets or streaming. Design should consider sharding/simulation partitioning, backpressure, and fault-tolerant persistence (event sourcing/CQRS) so you can recover and replay state.

You should demonstrate object-oriented design skills (encapsulation of Car, Door, Engine objects), use of State Pattern for lifecycle transitions, and Observer or pub/sub for monitoring and dashboard updates. Discuss concurrency controls (actor model vs optimistic locking), scaling strategies (worker pools, partition keys), latency considerations (<100ms target), and extensibility (interfaces/factories to add new simulation types or metrics). Finally, explain testing and stress strategies to validate thousands of simultaneous simulations and how to ensure reliability and no data loss under failures.