API Design Principles for Healthcare Systems

Healthcare APIs are different. They carry sensitive patient data, need to be available 24/7, and must integrate with legacy systems that were built when REST was just something you did after work.

Security First, Always

Authentication and Authorization
- Implement OAuth 2.0 with PKCE for public clients
- Use JWT tokens with short expiration times
- Implement role-based access control (RBAC) that maps to clinical roles

### Data Protection
- Encrypt everything in transit and at rest
- Implement field-level encryption for PHI
- Use tokenization for sensitive identifiers

## Performance Under Pressure

Healthcare systems can't afford downtime. Your API needs to handle:
- Sudden spikes during emergencies
- Graceful degradation when dependencies fail
- Sub-second response times for critical operations

### Caching Strategies
`javascript
// Example: Caching patient allergies with Redis
const getAllergies = async (patientId) => {
const cacheKey = allergies:${patientId};
let allergies = await redis.get(cacheKey);

if (!allergies) {
allergies = await database.getAllergies(patientId);
await redis.setex(cacheKey, 300, JSON.stringify(allergies)); // 5 min cache
}

return JSON.parse(allergies);
};
`

## Integration Challenges

### Legacy System Integration
Most hospitals run on systems from the 1990s. Your shiny new API needs to play nice with:
- HL7 v2 messages
- SOAP services
- Direct database connections (yes, really)

### Standards Compliance
- FHIR R4 for interoperability
- HIPAA for privacy
- SOC 2 for security controls

## Monitoring and Observability

In healthcare, you need to know about problems before they affect patient care:

`javascript
// Example: Health check endpoint
app.get('/health', async (req, res) => {
const checks = await Promise.allSettled([
checkDatabase(),
checkRedis(),
checkExternalAPIs()
]);

const status = checks.every(check => check.status === 'fulfilled')
? 'healthy' : 'degraded';

res.status(status === 'healthy' ? 200 : 503).json({
status,
timestamp: new Date().toISOString(),
checks: checks.map(check => ({
status: check.status,
value: check.value || check.reason
}))
});
});
`

## The Human Factor

Remember: your API serves real people taking care of real patients. Design with empathy, test thoroughly, and always prioritize patient safety over feature velocity.