What Is REST?
REST (Representational State Transfer) is an architectural style for building web APIs:
- General-purpose: Not healthcare-specific; used across all industries
- Flexible: No prescribed data model—design your own resources
- Widely adopted: Standard approach for most modern web APIs
- HTTP-based: Uses standard HTTP methods (GET, POST, PUT, DELETE)
REST Advantages
Simple, flexible, performant, widely understood by developers.
REST Limitations
No standard data model, requires custom integration for each system.
What Is FHIR?
FHIR (Fast Healthcare Interoperability Resources) is a healthcare-specific API standard:
- Healthcare-specific: Designed by HL7 for healthcare data exchange
- Standardized resources: Pre-defined data models for Patient, Condition, Observation, etc.
- Regulatory backing: Required by CMS for certain interoperability mandates
- Built on REST: Uses REST principles with healthcare data standards
150+
Pre-defined FHIR resources covering clinical, financial, and administrative data
Key Insight: FHIR is technically a type of REST API—it applies REST architectural principles with a standardized healthcare data model.
When to Use REST vs FHIR
REST
Choose REST When
- Building custom analytics applications
- Integrating internal systems with known schemas
- Performance is critical and data model is fixed
- Simpler implementation is preferred
FHIR
Choose FHIR When
- Exchanging data with external healthcare organizations
- Meeting CMS interoperability requirements
- Building EHR integrations via SMART on FHIR
- Long-term interoperability is a priority
Interoperability Considerations
Consider these factors when choosing between standards:
- Partner ecosystem: What standards do your integration partners support?
- Regulatory requirements: Does your use case require FHIR for compliance?
- Data complexity: Are you exchanging complex clinical data or simpler analytics?
- Development resources: FHIR has more structure but steeper learning curve
CMS Interoperability Mandates
CMS requires FHIR APIs for certain use cases:
- Patient Access API (member-facing data access)
- Provider Directory API (network information)
- Payer-to-Payer Data Exchange (plan transitions)
Future-Proofing Your API Strategy
A pragmatic approach to API selection:
Hybrid Approach
Use REST for internal analytics; FHIR for external exchange.
Translation Layer
Build adapters to convert between formats as needed.
Abstraction
Design internal systems to support multiple API formats.
Stay Current
Monitor regulatory developments and industry adoption.