How would you design Mint.com (personal finance aggregator)?

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Accepted Answer

## Step 1: Use Cases, Constraints, Assumptions, Back-of-Envelope

### Use cases
We'll scope to handle only the core flows that expose the bottlenecks; everything else is deferred.

- **User** links bank — OAuth/Finicity/Plaid flow, store encrypted tokens, test connection.
- **Service** syncs transactions — scheduled fetch (hourly/daily), normalize categories, dedupe by fit_id.
- **User** reads dashboard — aggregated balances, trends, budgets, search over normalized ledger.
- **Service** alerts — async rules (low balance, large spend) via notification queue.

### Out of scope
- Bill-pay execution, tax filing, credit-score modeling, PII beyond financial data.

### State assumptions
- 20M users, avg 3 linked institutions, 500 transactions/user/mo → 10B transactions total.
- Sync QPS: 20M*3/86k daily if hourly ≈700 fetches/s avg, bursty at top of hour 5k.
- Transaction 500 bytes → 10B*500≈5 TB + indexes 15 TB, per-user 15 KB/mo.
- Need bank-grade security (AES-256, HSM), 99.9% sync success

How would you design Mint.com (personal finance aggregator)?

Understand the problem

Attempt it yourself

Study the solution

Step 1: Use Cases, Constraints, Assumptions, Back-of-Envelope

Use cases

Solution ready — 2 min read

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STREAK ALIVE.

Understand the problem

Attempt it yourself

Study the solution

Step 1: Use Cases, Constraints, Assumptions, Back-of-Envelope

Use cases

Solution ready — 2 min read

Join the discussion

Discussion (0)

KEEP THESTREAK ALIVE.

KEEP THE
STREAK ALIVE.