[ OK ] 544 — full content available
[ INFO ] category: System Design difficulty: hard freq: high first seen: 2026-01-14
[HARD][SYSTEM DESIGN][HIGH]API DesignSecurityOAuthData AggregationFintechbackendinfrastructure
$ cat problem.md
Design a banking data aggregation API like Plaid's core product.
Source: Inferred from Plaid product and interview experiences
Requirements:
- Securely connect to multiple bank APIs
- Aggregate account and transaction data
- Handle OAuth authentication flows
- Ensure data privacy and compliance (PCI-DSS, SOC 2)
- Support rate limiting per user and per institution
- Handle bank API failures gracefully
Discussion Points:
- How would you implement token refresh in the background?
- How would you handle different authentication methods across banks?
- How would you ensure data consistency when a bank API is down?
- How would you design the API for third-party developers?