Q1. What is idempotency and which HTTP methods are idempotent?
An operation is idempotent when performing it multiple times produces the same server state as performing it once. - GET, HEAD, PUT and DELETE are idempotent by HTTP sema...
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Q2. Compare at-most-once, at-least-once and exactly-once delivery.
- At-most-once: the broker may deliver a message once or not at all. It never duplicates, so it can lose data. Achieved by acknowledging before processing. Suitable for m...
Q3. How do message queues help and what guarantees do they provide?
Queues decouple producers from consumers, absorb traffic spikes, enable retries and fan-out, and improve resilience when a downstream service is slow or down. Delivery se...
Q4. How do idempotency keys work for POST requests?
The client generates a unique key per logical operation and sends it in a header, typically `Idempotency-Key`. ```http POST /payments Idempotency-Key: 4d7c2e6a-2b1f-4f9a-...
Q5. What does idempotency mean in data pipelines and why does it matter?
An idempotent operation produces the same result whether it runs once or many times. Pipelines retry on failure, run backfills and get replayed, so non-idempotent logic c...
Q6. What makes a message consumer idempotent?
At-least-once delivery means duplicates will happen, so a consumer must produce the same result whether it sees a message once or several times. Techniques: - Deduplicati...
Q7. How would you write a robust, idempotent automation script?
A production script should be safe to re-run, fail clearly and clean up after itself. ```bash #!/usr/bin/env bash set -euo pipefail workdir=$(mktemp -d) cleanup() { rm -r...