Your question is Scalable Fault-Tolerant ETL. Take a moment with it on the right.
Talk me through your thinking if you like. When you're confident, submit your answer and I'll grade it like a real screen (7/10 or better passes).
What are the best practices for designing scalable and fault-tolerant ETL pipelines?
In a practical response, describe how you would choose batch or streaming execution, structure ingestion and transformation stages, and make processing idempotent. Cover orchestration, retries, checkpointing, schema evolution, data quality validation, observability, replay, backfilling, security, and cost control. Include a representative technology stack, an end-to-end architecture, and implementation examples that demonstrate safe recovery from partial failures.