HIPAA-Compliant Data Architecture: System Design Questions from Top HealthTech Firms

Problem Statement

HealthTech engineering interviews require designing secure systems that protect sensitive patient data while maintaining healthcare functionality. Candidates often struggle to balance strict HIPAA compliance requirements with scalable architectures, failing to address encryption, audit trails, and access controls comprehensively during interviews at companies like Epic, Oscar Health, and UnitedHealth Group.

HIPAA Compliance Overview

Healthcare applications must implement technical safeguards that protect electronic Protected Health Information (ePHI) while allowing authorized access. A practical approach focuses on these core requirements:

Core Architecture Components

A HIPAA-compliant system architecture requires specific components that enable secure data handling while maintaining proper access controls and audit capabilities:

When Oscar Health asks "How would you implement HIPAA-compliant data storage and transmission?", this diagram forms the foundation of your answer, outlining the separation of concerns and security boundaries.

PHI Data Handling Strategies

Data Classification Framework

Start your implementation with proper data classification to determine security requirements:

Encryption Implementation

A comprehensive encryption strategy must cover both data at rest and in transit:

For HIPAA-compliant field-level encryption implementation:

1function encryptPHI(data, fieldName) {
2  // Get data encryption key (DEK)
3  const dataKey = getOrGenerateDataKey();
4  
5  // Encrypt the PHI field with the data key
6  const encryptedField = encrypt(data[fieldName], dataKey.plaintext);
7  
8  // Encrypt the data key with the master key
9  const encryptedDataKey = encryptWithMasterKey(dataKey.plaintext);
10  
Show full code (19 lines)

Audit Trail Implementation

Epic Systems frequently asks candidates to "Design an audit system for tracking all access to patient records." An effective audit system must capture comprehensive metadata while remaining performant:

Audit Data Model

Audit System Architecture

A scalable audit system uses specialized components to ensure performance and compliance:

This architecture addresses these key requirements:

• Non-blocking event collection (crucial for medical systems)
• Immutable, tamper-evident audit storage
• Real-time alerting for suspicious access patterns
• Support for emergency "break glass" access scenarios

Access Control Systems

UnitedHealth Group often asks candidates to "Explain how you would handle PHI in a microservices architecture." Access control is a crucial component of the answer:

Access Control Model

A comprehensive PHI access control system includes multiple layers:

Example policy evaluation for healthcare-specific access rules:

1function evaluateAccessPolicy(user, resource, action, context) {
2  // Check role-based access
3  if (!hasRolePermission(user.roles, action, resource.type)) {
4    return { granted: false, reason: "INSUFFICIENT_ROLE" };
5  }
6  
7  // Check purpose-based access
8  if (!isValidPurpose(context.purpose, resource.type)) {
9    return { granted: false, reason: "INVALID_PURPOSE" };
10  }
Show full code (25 lines)

Microservices Architecture for PHI

For UnitedHealth Group's microservices question, your solution must address these key challenges:

PHI Gateway Pattern

The most effective approach for microservices handling PHI is the gateway pattern:

This pattern:

1. Centralizes PHI access and security controls
2. Minimizes PHI distribution across services
3. Simplifies compliance auditing
4. Reduces attack surface

Example PHI minimization in service-to-service communication:

1// BETTER: Using reference tokens and minimal necessary info
2function getAppointmentWithPatientInfo(appointmentId) {
3  const appointment = appointmentService.getAppointment(appointmentId);
4  const patientReference = patientService.getPatientReference(
5    appointment.patientId, 
6    { requiredFields: ['name', 'dob'], purpose: 'APPOINTMENT_DISPLAY' }
7  );
8  return { ...appointment, patientReference };
9}

Secure Data Sharing Between Providers

Epic frequently asks candidates to "Design a secure system for sharing patient data between healthcare providers." An effective solution must address both technical and regulatory challenges:

This implementation highlights:

• Explicit consent verification before sharing
• End-to-end encryption for data in transit
• Purpose-limited data packages (minimum necessary principle)
• Audit logging at every step of the sharing process

Key Takeaways

• Defense in Depth: Implement multiple layers of security for PHI protection
• Encryption Everywhere: Apply encryption at rest, in transit, and between services
• Comprehensive Auditing: Track all PHI access with detailed context information
• Granular Access Control: Implement role, purpose, and relationship-based controls
• Minimum Necessary: Share only the minimum PHI required for each specific purpose

HIPAA-Compliant Architecture Decision Framework

Download our comprehensive HIPAA-compliant architecture decision tree to guide your HealthTech system design process and prepare for technical interviews.

The framework includes:

• PHI classification workflow
• Access control decision trees
• Encryption implementation patterns
• Audit requirements matrix
• Microservices security guidelines

Download Framework →

Sources

1. HHS HIPAA Security Rule, Technical Safeguards: https://www.hhs.gov/hipaa/for-professionals/security/laws-regulations/index.html
2. NIST Guide to HIPAA Security Rule: https://nvlpubs.nist.gov/nistpubs/Legacy/SP/nistspecialpublication800-66r1.pdf
3. Healthcare API Security Best Practices: https://www.hl7.org/fhir/security.html
4. OWASP Top 10 for Healthcare Applications: https://owasp.org/www-project-top-10-for-healthcare-apps/
5. Microservices Security Patterns for Healthcare: IEEE Conference on Cloud Engineering (IC2E)