How do I approach System Design interview questions?

System Design questions require understanding of core concepts and practice. PracHub provides solutions with explanations to help you master system design interviews.

What difficulty level is this interview question?

This is a hard difficulty System Design question, commonly asked during Technical Screen rounds at Perplexity AI.

What role is this question designed for?

This question is commonly asked for Software Engineer candidates at Perplexity AI during technical interviews.

Design a personal finance aggregator | Perplexity AI Interview Question

Quick Overview

This question evaluates skills in large-scale system design including API and third-party integrations, data ingestion and normalization, transactional consistency and idempotency, security and privacy controls, data modeling for multi-currency financial records, and operational concerns like alerts and budgeting.

System Design: Personal Finance Aggregation Platform (Mint-like)

Context

Design a consumer-facing platform that aggregates a user's financial data across banks, credit cards, loans, and other institutions. The system ingests balances and transactions, normalizes data, categorizes spending, supports budgeting, and provides alerts. Assume a modern technical screen context and aim for a pragmatic, production-ready design.

Assumptions (minimal):

Scale: 1–5M users, each with 2–6 linked accounts; daily ingestion volume in the tens of millions of transactions.
Data freshness: near-real-time via webhooks where available; otherwise periodic polling (e.g., hourly to daily).
Regions: initially single region with future multi-region readiness.

Requirements

API/ingestion: choose aggregator vs. direct connections; authenticate via OAuth/Open Banking where possible; legacy OFX if needed.
Data processing: normalization and deduplication across sources; consistent signs and timestamps.
Categorization and budgeting: rules/ML categorization; budgets by category with rollovers and sharing.
Alerts/notifications: thresholds, anomalies, upcoming bills; delivery via push/email/in-app.
Reconciliation and idempotency: pending-to-posted transitions, retries, and exactly-once semantics.
Privacy/security: encryption, tokenization, consent, PCI scope minimization.
Scalability/storage: service boundaries, data stores, partitioning, and caching.
Failure/latency handling: third-party API slowness/outages, rate limits, backoff, and graceful degradation.
Data model: consistent schema supporting multi-currency and recurring bills/subscriptions.

Quick Overview

Context

Assumptions (minimal):

Scale: 1–5M users, each with 2–6 linked accounts; daily ingestion volume in the tens of millions of transactions.

Data freshness: near-real-time via webhooks where available; otherwise periodic polling (e.g., hourly to daily).

Regions: initially single region with future multi-region readiness.

Requirements

API/ingestion: choose aggregator vs. direct connections; authenticate via OAuth/Open Banking where possible; legacy OFX if needed.

Data processing: normalization and deduplication across sources; consistent signs and timestamps.

Categorization and budgeting: rules/ML categorization; budgets by category with rollovers and sharing.

Alerts/notifications: thresholds, anomalies, upcoming bills; delivery via push/email/in-app.

Reconciliation and idempotency: pending-to-posted transitions, retries, and exactly-once semantics.

Privacy/security: encryption, tokenization, consent, PCI scope minimization.

Scalability/storage: service boundaries, data stores, partitioning, and caching.

Failure/latency handling: third-party API slowness/outages, rate limits, backoff, and graceful degradation.

Data model: consistent schema supporting multi-currency and recurring bills/subscriptions.

Design a personal finance aggregator

Quick Overview

System Design: Personal Finance Aggregation Platform (Mint-like)

Context

Requirements

Solution

Submit Your Answer

Design a personal finance aggregator

Quick Overview

System Design: Personal Finance Aggregation Platform (Mint-like)

Context

Requirements

Solution

Submit Your Answer