Technical Architecture

REV.health is built on 9 interlocking subsystems spanning cloud infrastructure, data, AI/ML, mobile, identity, resilience, and audit.

9 Subsystems Overview

1. Cloud Infrastructure

Azure (primary): Cosmos DB (OLTP), Azure OpenAI, Microsoft Fabric (analytics/ETL).

AWS (secondary): HealthLake (FHIR store), MSK/Kafka (event streaming), S3 (document store with Object Lock), Bedrock (fallback LLM inference).

2. Multi-Tenancy

Tier	Isolation	Data Strategy	Target Org Size
T1 — Standard	Partition key	Shared Cosmos database, OrganizationID partition	Small & mid practices
T2 — Dedicated DB	Database-level	Dedicated Cosmos database per org, shared account	Large groups & MSOs
T3 — Dedicated Account	Account + VNet	Dedicated Cosmos account, isolated VNet, customer-managed keys	Health systems & enterprise

3. Data Architecture

OLTP: Azure Cosmos DB (NoSQL API) — partition-key multi-tenancy
FHIR facade: FHIR R4 read/write over Cosmos documents
Event store: Kafka (MSK) — append-only clinical event log
Document store: S3 with Object Lock (WORM) for scanned documents, consent forms, attachments
Analytics: ClickHouse for real-time operational analytics; Microsoft Fabric for batch ETL & reporting

4. API Design

FHIR R4 + US Core 7.0.0
SMART on FHIR v2.2.0
Bulk Data Access v2.0.0
CDS Hooks 2.0
Da Vinci Implementation Guides (PAS, CRD, DTR, PDex, HRex)
gRPC for internal service-to-service communication

5. AI/ML Pipeline

All clinical AI flows through a governed 5-stage pipeline:

Redaction Gateway — strip/tokenize PHI before LLM inference
LLM Gateway — route to Azure OpenAI or Bedrock based on load/cost/capability
Domain Models — fine-tuned models for coding, NLP, scribe, CDS
Human-in-the-Loop — clinician review queues for AI suggestions above confidence threshold
Governance Committee — quarterly model audit, bias review, performance metrics

6. Mobile

Clinician: iPad-first responsive web app (Angular 21, PWA)
Patient: React Native / Flutter native app (iOS + Android)

7. IAM (Identity & Access Management)

SAML 2.0 / OIDC SSO federation
AAL2 for clinical access; AAL3 for EPCS (biometric + hardware token)
RBAC + ABAC hybrid — role grants base permissions, attribute policies refine per context

8. Resilience & DR

Service Tier	RTO	RPO	Examples
Tier 1 — Critical	4 hours	5 minutes	Clinical documentation, eRx, scheduling, patient portal
Tier 2 — Important	24 hours	1 hour	Analytics, reporting, bulk data export, batch jobs

9. Audit & Logging

Hash-chained append-only audit log
Archived to S3 Object Lock (WORM compliance)
10-year retention policy (HIPAA + state mandates)
Every clinical data read/write produces an audit entry with actor, resource, justification, and authorization chain

Architecture Diagram

graph TD
  subgraph Client["Client Layer"]
    CL1["Angular 21 PWA
(Clinician)"]
    CL2["React Native / Flutter
(Patient)"]
    CL3["Third-party Apps
(SMART on FHIR)"]
  end

  subgraph Edge["Edge Layer"]
    CDN["Component CDN"]
    WAF["WAF / DDoS"]
    APIGW["API Gateway"]
  end

  subgraph App["Application Layer"]
    FHIR["FHIR R4 Facade"]
    AUTH["IAM / SSO"]
    AI["AI/ML Pipeline"]
    CDS["CDS Hooks Engine"]
    GRPC["gRPC Services"]
  end

  subgraph Data["Data Layer"]
    COSMOS["Cosmos DB
(OLTP)"]
    KAFKA["Kafka / MSK
(Event Store)"]
    S3["S3 Object Lock
(Documents)"]
    CH["ClickHouse
(Analytics)"]
    FABRIC["Microsoft Fabric
(ETL)"]
  end

  CL1 --> CDN
  CL2 --> APIGW
  CL3 --> APIGW
  CDN --> WAF --> APIGW
  APIGW --> FHIR
  APIGW --> AUTH
  APIGW --> AI
  APIGW --> CDS
  FHIR --> GRPC
  CDS --> GRPC
  AI --> GRPC
  GRPC --> COSMOS
  GRPC --> KAFKA
  GRPC --> S3
  KAFKA --> CH
  KAFKA --> FABRIC