← Sigmacomputing Interview Insights
The core concept clicked pretty quickly for me since it's basically a queue wrapped around promises.
Start by clarifying the requirements: tasks should execute in the order they are called, regardless of their individual delays. Then, propose a solution using a queue to maintain order and a mechanism to ensure only one task runs at a time, such as a promise chain or a lock. Finally, discuss trade-offs like error handling and concurrency.
Pro tip: Mention that this pattern is similar to a sequential promise queue, and highlight that it ensures deterministic execution order, which is crucial for UI updates and avoiding race conditions.
Confirm that tasks should run in the order they are invoked, even if they have different delays, and that only one task should run at a time.
Use a queue to store tasks in the order they are called. Each task includes a callback and its delay.
Use a promise chain or a lock to ensure that the next task starts only after the previous one completes, preserving order.
Consider error handling, cancellation, and dynamic addition of tasks while the queue is running.
Compare this approach to parallel execution, noting benefits like order guarantee and drawbacks like increased total time.
AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.
This is where things got genuinely tricky.
Clarify the concurrency model and the meaning of 'order of timeouts' (e.g., earliest timeout first). Then propose a design that preserves the global order of run_task calls while allowing tasks within a single call to be scheduled by timeout, using a priority queue per call and a global queue for call order.
Pro tip: Mention that you would first confirm whether tasks within a call should run concurrently or sequentially, and whether timeouts are fixed or dynamic; this shows you think about edge cases and avoid over-engineering.
Ask about the concurrency model, whether tasks within a call can run in parallel, and how timeouts are defined (e.g., absolute deadlines or relative durations). Confirm that the order between separate run_task calls must be strictly preserved.
Use a global FIFO queue to maintain the order of run_task calls. For each call, use a min-heap (priority queue) keyed by timeout to order tasks within that call.
Process calls in FIFO order. For each call, extract tasks from its min-heap in timeout order and execute them, ensuring that no task from a later call starts before all tasks from the current call are scheduled.
Consider if tasks within a call can run concurrently; if so, use a thread pool or async execution while still respecting timeout order for starting tasks. Handle empty lists, duplicate timeouts, and dynamic timeout changes.
Discuss time complexity: O(n log n) for sorting tasks within each call, and O(m) for processing m calls. Mention alternative approaches like sorting the list if timeouts are static, and trade-offs between simplicity and performance.
AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.