NURO·Software Engineer·Technical Phone Screen·Senior

SeniorPrefer not to say

Jun 2026Remote

Summary

Nuro interview that was more hands-on than I expected. They gave me a concurrent systems problem and wanted actual running code, not pseudocode or a whiteboard sketch.

Questions Asked (1)

Build a periodic job scheduler that takes a task function and a frequency in Hz, converts that to a time interval, and runs the task on that cadence. It needs a schedule(task, hz) and cancel(handle) API, must use separate threads for scheduling and execution, and has to actually run correctly with proper thread safety and clean shutdown.

System DesignTechnical Trade-offsAlgorithms & Data Structures

Author's notes

The part that tripped me up was the cancel logic.

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AI HintsAI Generated

Suggested Approach

Start by clarifying requirements and constraints, then design a thread-safe scheduler using a priority queue or timing wheel, with separate threads for scheduling and execution. Walk through the API design, synchronization mechanisms, and clean shutdown, and discuss trade-offs and potential pitfalls.

Pro tip: Emphasize how you handle task overruns and missed executions—this shows you understand real-world scheduling challenges beyond the happy path.

1. Clarify Requirements and Constraints

Ask about expected precision, task duration, number of tasks, and whether tasks can run concurrently. Confirm that frequency is in Hz and that cancel should stop future executions.

2. Design the Scheduler Architecture

Propose a design with a scheduler thread that manages a priority queue of tasks ordered by next execution time, and a separate thread pool for executing tasks. Explain how schedule and cancel interact with the queue.

3. Implement Thread Safety and Synchronization

Use locks or concurrent data structures to protect shared state. Ensure that schedule and cancel can be called from any thread without corrupting the queue.

4. Handle Execution and Timing

Describe how the scheduler thread waits until the next task's time, then dispatches it to an executor. Discuss how to handle task overruns (e.g., skip or delay next execution) and maintain cadence.

5. Ensure Clean Shutdown

Provide a shutdown method that stops the scheduler thread, cancels pending tasks, and gracefully shuts down the executor, ensuring no tasks are left running or resources leaked.

Key Points to Mention

Use of a priority queue (min-heap) to efficiently retrieve the next task to execute.
Separate threads: one for scheduling (waiting and dispatching) and a thread pool for executing tasks.
Thread safety via locks (e.g., ReentrantLock) or concurrent collections, and atomic operations for handle management.
Handling task overruns: decide whether to skip, delay, or run concurrently, and document the chosen policy.
Clean shutdown: interrupt scheduler thread, cancel all tasks, and await termination of executor.
API design: schedule returns a handle (e.g., unique ID or object) that can be passed to cancel; cancel removes the task from the queue and prevents future executions.

AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.