# A subscription company runs Postgres signups -> daily Python ETL -> Snowflake daily_signups_by_count

Canonical URL: <https://datadriven.io/problems/a-subscription-company-runs-postgres-signups-daily-python-26d7d54e>

Domain: Pipeline Design · Difficulty: medium

## Problem

A subscription company runs Postgres signups -> daily Python ETL -> Snowflake daily_signups_by_country -> Looker. Marketing then asks for the chart redrawn under a new country grouping for the last 18 months. The team kicks off a backfill and discovers Postgres holds only the last 90 days. Apply the section's four-layer framing and add the missing layer that would make the 18-month backfill possible.

## Related

- [All practice problems](https://datadriven.io/problems)
- [Mock interview mode](https://datadriven.io/interview/a-subscription-company-runs-postgres-signups-daily-python-26d7d54e)
- [System Design Interview Questions](https://datadriven.io/data-engineering-system-design)
- [Data Engineering Interview Prep Guide](https://datadriven.io/data-engineer-interview-prep)
- [Daily Challenge](https://datadriven.io/daily)

---

Source: DataDriven (https://datadriven.io). 100% free data engineering interview prep. Live code execution against Postgres 16, Python 3.11, and Spark sandboxes. No paywall, no premium tier, no signup gate.