In a scenario where data is in JSON, why would you use CSV? Why use one-phase CSV and other JSON?

JSON is hierarchical and supports nested objects, making it ideal for APIs and semi‑structured data. CSV is flat, tabular, and lightweight, which makes it efficient for bulk loading into relational databases or spreadsheets. When data originates as JSON but downstream systems expect a table, converting to CSV can reduce parsing overhead and simplify schema enforcement. One‑phase CSV usage is common when the entire pipeline deals with simple, flat data – for example, a CSV file is ingested, transformed, and loaded directly into a data warehouse. In contrast, a two‑phase approach might use CSV for staging (fast ingestion) and JSON for the final format when the data needs to preserve nested relationships or be consumed by a NoSQL store. Choosing the format depends on the structure of the data, the capabilities of the target system, and performance considerations.