Design mobile check deposit system

Q: Design mobile check deposit system

This question evaluates a candidate's ability to design end-to-end, production-grade mobile check deposit systems, assessing competencies in system architecture, distributed systems, security and fraud prevention, regulatory compliance (Reg CC, Check 21), data durability, and operational observability.

Q: 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.

Q: What difficulty level is this interview question?

This is a hard difficulty System Design question, commonly asked during Onsite rounds at Chime.

Q: What role is this question designed for?

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

Question

System Design: Mobile Check Deposit for a Consumer Banking App

Context

Design a production-grade Remote Deposit Capture (RDC) feature that allows retail customers to deposit paper checks using a mobile app in the U.S. banking context. The system must be secure, compliant with U.S. regulations (Reg CC, Check 21), resilient, and scalable.

Requirements

Functional Requirements

Capture and guidance
- On-device capture of front and back images with guidance overlays.
- Auto-capture when alignment, focus, and lighting thresholds are met.
- On-device prechecks: glare/blur detection, edge and MICR line presence, endorsement presence on back.
Amount entry and validation
- User enters amount; server validates via OCR (CAR/LAR) and MICR context; handle mismatches.
Duplicate and limit checks
- Detect duplicates within institution and across users/devices; integrate with external duplicate networks if available.
- Enforce per-deposit, daily, and rolling limits by user/account/risk tier.
Deposit status lifecycle
- Statuses with clear transitions, e.g., Created → Uploaded → Processing → Accepted → Pending Hold → Available, or Rejected/Returned.
Notifications
- In-app real-time updates, push notifications, and email for acceptance, holds, availability, rejections, and returns.
Error handling
- User-friendly retries for capture/upload; server-side retries with backoff; dead-letter queues for poison messages.

Non-Functional Requirements

Availability: 99.9%+ for submission API; 99.95% for status reads.
Latency: P50 < 300 ms and P95 < 800 ms for submission acknowledgement; near-real-time processing with eventual completion minutes-scale.
Durability: Image and transaction data ≥ 11 nines for images (multi-region object storage); transactional durability for ledger writes.
Consistency: Strong consistency for idempotency, limit checks, and ledgering; eventual consistency acceptable for notifications and analytics.
Observability: End-to-end traces, structured logs with PII scrubbing, SLO dashboards, anomaly detection on failure rates and OCR quality.

Risk and Compliance

Fraud prevention: device fingerprinting, velocity limits, risk scoring, liveness/attestation checks, endorsement verification, duplicate networks.
Holds and funds availability: Reg CC-compliant schedules; risk-adjusted holds; cutoff times; disclosures.
Check 21: image quality and exchange standards (X9.37), MICR integrity, CAR/LAR validation.
Audit trails: immutable, tamper-evident logs; retention per policy (e.g., 7 years).
PII protection: encryption in transit/at rest, access controls, data minimization, redaction/masking, key management and rotation.

Architecture Scope

Propose end-to-end design covering: on-device capture and guidance; image preprocessing (dewarp, glare/blur detection); MICR/OCR pipeline; endorsement verification; limits and risk scoring; duplicate detection across users/devices; idempotent submission API; asynchronous processing and reconciliation; core banking integration and ledgering; error handling with retries and dead-letter queues. Discuss data models, APIs, storage, scaling, rate limiting, device fingerprinting, security, monitoring, and testing strategies (sandbox, golden datasets, canary releases).

Design mobile check deposit system

Quick Overview

System Design: Mobile Check Deposit for a Consumer Banking App

Context

Requirements

Functional Requirements

Non-Functional Requirements

Risk and Compliance

Architecture Scope

Solution

Comments (0)

Design mobile check deposit system

Quick Overview

System Design: Mobile Check Deposit for a Consumer Banking App

Context

Requirements

Functional Requirements

Non-Functional Requirements

Risk and Compliance

Architecture Scope

Solution

Comments (0)