Two Wallets

A medium Data Modeling interview practice problem on DataDriven. Write and execute real data modeling code with instant feedback.

Domain

Data Modeling

Difficulty

medium

Seniority

L5

Problem

We run an online education marketplace with two user types: students paying for access, and instructors paying for listing and promotion features. Both subscribe to different plan tiers and keep several payment methods on file, each stored as an opaque gateway token plus the card brand and last four digits for display, never full card numbers. Finance also needs to reconstruct how many subscribers we had in any past month, so design the data model behind billing.

Summary

Two user types. Multiple payment methods. One messy billing table.

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