The sequential part was fine, just a loop with awaits.
Start by outlining a simple sequential implementation: iterate over the array, assign color based on latitude, and await each POST before moving to the next. Then explain how to parallelize using a bounded concurrency pattern (e.g., a worker pool or semaphore) to limit simultaneous requests, while handling errors and rate limits gracefully.
Pro tip: Mention that Stripe's API has rate limits and idempotency keys; using idempotency keys ensures safe retries, and respecting rate limits avoids 429 errors. Also, consider using a library like p-limit for bounded concurrency in Node.js.
Ask about array size, API rate limits, error handling expectations, and whether order matters. This shows you think about production concerns.
Describe a simple loop with await: for each coordinate, determine color (latitude >= 0 ? 'red' : 'blue'), then POST {coordinate, color} to the endpoint. Handle errors per request.
Note that sequential is slow for large arrays and doesn't utilize network concurrency, but it's simple and avoids overwhelming the API.
Explain using a concurrency limit (e.g., 5-10) via a worker pool, semaphore, or library like p-limit. Process items in parallel but cap in-flight requests.
Cover retry logic with exponential backoff for transient errors, and use idempotency keys to avoid duplicate POSTs. Consider logging failures for later reprocessing.
AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.
Blanked for a second on idempotency keys specifically.
Start by acknowledging that transient failures are inevitable in distributed systems, then outline a robust retry strategy with exponential backoff and jitter, and emphasize idempotency as the key to safe retries. Conclude by discussing how to monitor and test these mechanisms to ensure reliability.
Pro tip: Mention that Stripe supports idempotency keys via the 'Idempotency-Key' header, and that you should generate a unique key per request and reuse it on retries. Also, highlight the importance of not retrying on non-idempotent errors like 400 Bad Request, as that could lead to duplicate operations.
Explain that transient failures include network timeouts, 5xx server errors, and rate limiting (429). Distinguish these from permanent failures like 4xx client errors.
Describe using exponential backoff with jitter to avoid thundering herd, and set a maximum number of retries. Mention libraries or built-in support (e.g., Stripe SDK's automatic retries).
Use idempotency keys (e.g., UUIDs) for each unique request, and include them in the header. Explain that the server should deduplicate based on these keys to prevent duplicate side effects.
Only retry idempotent operations or those with idempotency keys. For non-idempotent operations, consider alternative strategies like checking status before retrying.
Discuss logging retries, monitoring failure rates, and testing with fault injection to ensure the retry logic works as expected.
AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.