Design a personal-finance platform like Mint.com: let users link bank, credit-card, loan, and investment accounts via a third-party aggregator (Plaid/Yodlee), sync and store transactions across all accounts, deduplicate them (including pending→posted transitions and corrections), auto-categorize spend, support user-defined per-category budgets with alerts, and serve a low-latency spending-analytics and net-worth dashboard — all under security (PII/credential handling), high-availability, consistency, and latency constraints. The interview lives in transaction sync + dedup + categorization, not CRUD.
Naive approach with serious trade-off — being authored.
Solid baseline with reasonable trade-offs — being authored.
Production-grade approach with explicit trade-off rationale — being authored.
Naive approach with serious trade-off — being authored.
Solid baseline with reasonable trade-offs — being authored.
Production-grade approach with explicit trade-off rationale — being authored.
Naive approach with serious trade-off — being authored.
Solid baseline with reasonable trade-offs — being authored.
Production-grade approach with explicit trade-off rationale — being authored.
Naive approach with serious trade-off — being authored.
Solid baseline with reasonable trade-offs — being authored.
Production-grade approach with explicit trade-off rationale — being authored.
Naive approach with serious trade-off — being authored.
Solid baseline with reasonable trade-offs — being authored.
Production-grade approach with explicit trade-off rationale — being authored.
Cover happy path. Clarify scope. Identify the obvious bottleneck. Pick a reasonable storage and reasonable scaling approach.
All of the above plus: explicit failure handling, durability vs latency trade-offs, choose the right batching/caching strategy, articulate why.
All of the above plus: organizational concerns (rollout, migration, on-call), quantitative analysis, multi-region considerations, what could go wrong with the proposed solution at 10x scale.
Passing patterns: structure functional vs non-functional requirements first; name Plaid/Yodlee + the OAuth token model; give a concrete dedup strategy (external_tx_id upsert + fuzzy fallback); propose event-driven (Kafka) decoupling of sync/categorization/alerting; pre-aggregate + cache for dashboards. Failing patterns: diving into low-level details before scoping; treating Mint as a CRUD app; skipping security/PII entirely.